/sqt/ - stupid questions thread (aka /qtddtot/)

[Anonymous No.16109209]

Previous thread: >>16085923

>what is /sqt/ for?
Questions regarding maths and science. Also homework.
>where do I go for advice?
>>>/sci/scg or >>>/adv/
>where do I go for other questions and requests?
>>>/wsr/ >>>/g/sqt >>>/diy/sqt etc.
>how do I post math symbols (Latex)?
rentry.org/sci-latex-v1
>a plain google search didn't return anything, is there anything else I should try before asking the question here?
scholar.google.com
>where can I search for proofs?
proofwiki.org
>where can I look up if the question has already been asked here?
warosu.org/sci
eientei.xyz/sci
>how do I optimize an image losslessly?
trimage.org
pnggauntlet.com
>how do I find the source of an image?
images.google.com
tineye.com
saucenao.com
iqdb.org

>where can I get:
>books?
libgen.rs
annas-archive.org
stitz-zeager.com
openstax.org
activecalculus.org
>articles?
sci-hub.st
>book recs?
sites.google.com/site/scienceandmathguide
4chan-science.fandom.com/wiki//sci/_Wiki
math.ucr.edu/home/baez/physics/Administrivia/booklist.html
>online courses and lectures?
khanacademy.org
>charts?
imgur.com/a/pHfMGwE
imgur.com/a/ZZDVNk1
>tables, properties and material selection?
www.engineeringtoolbox.com
www.matweb.com
www.chemspider.com

Tips for asking questions here:
>avoid replying to yourself
>ask anonymously
>recheck the Latex before posting
>ignore shitpost replies
>avoid getting into arguments
>do not tell us where is it you came from
>do not mention how [other place] didn't answer your question so you're reposting it here
>if you need to ask for clarification fifteen times in a row, try to make the sequence easy to read through
>I'm not reading your handwriting
>I'm not flipping that sideways picture
>I'm not google translating your spanish
>don't ask to ask
>don't ask for a hint if you want a solution
>xyproblem.info

[Anonymous No.16109334]

>>16109209
If the universe is in a hole, why?

[Anonymous No.16109363]

How do lgbt transisters work?

[Anonymous No.16109546]

>>16109334
Explain what makes you believe the universe is in a hole?

[Anonymous No.16109551]

True or BS?

[Anonymous No.16109562]

>>16109551
A click bait title misinterpreting a scientific fact. Somewhere between 5 to 20 times as much water exists below the earth's surface than above it, and that includes the oceans. However it is not flowing in great underground seas, instead it's trapped under pressure within the rocks of the mantle.

[Anonymous No.16109716]

If [math] f : \mathbb{R} \rightarrow \mathbb{R} [/math] is a function, and f is differentiable on [math] \mathbb{R}\setminus\{0\} [/math],
and if the two-sided limit [math] \lim_{x\to 0} f ' (x) [/math] exists (and is finite) and equals say L , then is f differentiable at x=0 with derivative f ' (0)=L ?

[Anonymous No.16109771]

>>16109716
You mean like the Heaviside function?
That one is still not differentiable in 0.

[Anonymous No.16109891]

>>16109716
>>16109771
Oops I forgot to add the condition that f(x) is continuous at x=0;

Then is it true?

[Anonymous No.16109893]

Does anyone know the reaction products of Solanine and Acetic Acid? My Google-fu has failed me.

[Anonymous No.16109914]

>>16109891
no
consider [math]f(x)=|x|[/math]

[Anonymous No.16109917]

>>16109914
That does not have the two sided limit of f ‘(x) existing at x=0 ; read >>16109716 again

[Anonymous No.16109940]

>>16109917
Yeah, sorry, I misread that as being the limit of [math]f(x)[/math] itself.
In that case, the answer is yes, following from applying the mean-value theorem to [math]f'(x)[/math]

[Anonymous No.16109942]

>>16109917
sorry, misread that as discussing the limit of [math]f(x)[/math].
In that case, the answer is yes, by applying the mean-value theorem

[Anonymous No.16110015]

>>16109209
I'm confused when it comes to random variables and samples. if you have a random variable X, I understand that the expectation of any sample (X1, X2, X3, XN) equals just the expectation of X. But I don't understand the variance, why is the expected variance of the sample equal to the variance of the variable? I found a proof online but it uses σ^2 = E(xi^2)−μ^2, which is already something I don't understand.

[Anonymous No.16110314]

if f is continuous in [a,b], is saying that b-a is not equal to 0 enough to explain why this function is continuous or do I need to explain it more?

[Anonymous No.16110317]

>>16109209
highschool dropout here, I need to get my ged but I'm really struggling with one math concept, doing an equation on both sides. None of the videos on youtube I've watched have helped at all it just all feels unintuitive to me, any links to resources? kahn academy hasn't helped.

[Anonymous No.16110356]

What is it that sustains the back-and-forth of personal attacks on 4chan? Example >>16110348
It would be understandable if the argument contained an actual point of disagreement, since the debate could be witnessed by third parties who may draw the "wrong" conclusion if not corrected. But no one benefits from this kind of posts, not even the anons making them, because they're not tripfagging and so can always do picrel with no loss of reputation anyway.

[Anonymous No.16110358]

>>16110356
Forgot pic

[Anonymous No.16110433]

>>16109363
*IGBT transistors

[Anonymous No.16110627]

I'm looking for examples of countable abelian groups which are *not* finitely generated, preferably topological groups which are naturally discrete ([math]\mathbb{Q}[/math] being a prominent non-example).

Any ideas?

[Anonymous No.16110633]

how the fuck do i learn electromagnetism? Feynman lectures read like gibberish am i getting filtered

[Anonymous No.16110641]

>>16110633
I don't know anything about Feynman lectures but pic rel is an awesome book

[Anonymous No.16110647]

>>16110433
it's just a high current FET driven by a BJT, isn't it? or vice versa

[Anonymous No.16110651]

>>16110633
ignore physicists, build RF curcuits
don't bother with calculus slop until you're an expert at physical construction

[Anonymous No.16110657]

>>16110627
(G[X],+) where G is any finite or countable abelian group?

[Anonymous No.16110678]

>>16110627
I'm not sure what you mean with "naturally discrete", any abelian group is a topological group with the discrete topology, no?
The most "natural" example I can think of is functions
[math]\mathbb{N} \to \mathbb{Z}[/math] with finite support.

[Anonymous No.16110682]

>>16109716
>>16109891
This is L'Hôpital's rule.

[Anonymous No.16110696]

>>16110641
i read a few paragraphs but it seems very good. i'm going to use it, thanks anon.
>>16110651
i just need to pass my stupid exam

[Anonymous No.16110735]

>>16110696
>muh exams
drop out faggot

[Anonymous No.16110771]

>>16110678
cute wemi

[Anonymous No.16110783]

>>16110735
I study CS.
Nuff said

[Anonymous No.16110801]

Do we have the ability to burn polyunsaturated fat as fuel? Is it easier for the body to burn saturated fat than other fats?

This is not a homework question. I am working on my health.

[Anonymous No.16110821]

>>16110682
Wrong lmao

[Anonymous No.16110835]

>>16110801
Calories in, calories out. Don’t be a moron that cuts things out of your diet unless there is a gastrointestinal or religious reason. You can eat almost anything, and as long as you’re at a safe calorie deficit, you’ll lose weight.

[Anonymous No.16110845]

>>16110821
?
[math]\lim\limits_{x\to0}\frac{f(x)-f(0)}{x}=\lim\limits_{x\to0}f'(x)=L[/math].
Did I get baited?

[Anonymous No.16110882]

>>16110835

Saturated fat in, heart attacks out. I'm not asking for losing weight purposes. I didn't say i am working on my weight, i said i'm working on my health. Try reading before you shit out a standard reply.

[Anonymous No.16110904]

>>16110845
Anon you need to look at the conditions of LH's rule more carefully.

See condition 4 at https://en.wikipedia.org/wiki/L%27H%C3%B4pital%27s_rule#Cases_where_theorem_cannot_be_applied_(Necessity_of_conditions)

Using LH's rule on [math] \lim_{x\to c} f(x)/g(x) [/math] is only allowed if [math] \lim_{x\to c} f ' (x)/g ' (x) [/math] is *already known to exist* .

[Anonymous No.16110907]

>>16110904
Actually no sorry, I'm completely retarded, ignore this

You're right, LH's rule works here.

[Anonymous No.16110913]

>>16110907
np, it happens.

[Anonymous No.16111051]

Real analysis, complex analysis are taught in 2,3rd year of our engineering degree. Is it anyhow applicable in the field of computer science (I know problem solving skills are necessary but still just curious, I kinda enjoy proof based maths, discrete maths, calc etc) ? Like in what particular branches of CSE it can be used ? Other than mathematical, financial modeling

[Anonymous No.16111074]

>>16110882
>Saturated fat in, heart attacks out.
stop reading ancel keys' propaganda

[Anonymous No.16111124]

>>16110317
Whatever you do to one side, you do to the other. It's all about balancing quantities on both sides.
e.g.,
2x - 3 = 10
You really just do the opposite of pedmas, in order to solve for x.
1. undo the shifting operations (+,-)
2x -3 +3 = 10 +3
2. undo the scaling operations (*,/)
2*x /2 = 13 /2

finally, any number over itself is just a fancy way of saying 1, so 2/2 = 1 implies x = 13/2

[Anonymous No.16111131]

>>16111111

[Anonymous No.16111533]

>>16109893
Do they react?
I can think of three ways it can go:
>protonate the amine and get the acetate salt
>dehydrate the sugar (somewhere) and get water plus a smaller saponin
>hydrate the double bond and get a hydroxyl on the steroid

[Anonymous No.16111535]

>>16110015
The "Definition" section of the Wikipedia page for Variance has a proof of Var(X) = E(X2) - (E(X))2

[Anonymous No.16111573]

If [math] \vec{r} (t) [/math] is a smooth curve in [math] \mathbb{R}^3 [/math], with principal unit normal vector [math] \vec{N}(t) [/math] [assumed to exist at all times t],

then does [math] \vec{N}(t) [/math] also equal the unit vector in the direction of the perpendicular component of acceleration?

[Anonymous No.16111623]

>>16111573
the acceleration is pointed at some arbitrary direction. If u want to decompose it into components parallel to N, and components perpendicular to N, that's your choice to do so. Just tilt ur head and you can decompose it into any three orthogonal directions you want.

[Anonymous No.16111646]

>>16111623
Quick google search shows I was right:
https://courses.lumenlearning.com/calculus3/chapter/components-of-the-acceleration-vector/

The decomposition of acceleration given there clearly shows that N is indeed the unit vector in the direction of the perpendicular component of acceleration.

[Anonymous No.16111656]

What would happen if you used an air compressor in an airtight room?

[Anonymous No.16111720]

In statics we use two symbols, both triangles but one has a circle on top. What are they called and what are they used for?

[Anonymous No.16111722]

>>16111656
good q desu

[Anonymous No.16111728]

>>16111722
The ground became wavy/watery

[Anonymous No.16111735]

>>16111728
huh anon?

[Anonymous No.16111839]

>>16111720
anons i have an exam pretty soon

[Anonymous No.16111961]

>>16109209
How do you solve this? All I get is 1.15 m which doesn't make sense.

[Anonymous No.16111978]

>>16110314
also how do I know that if f is continous at [a,b] then l(x)=x-a is continuous?

[Anonymous No.16111981]

>>16111978
Continuous functions form an Algebra so sums and products of continuous functions are continuous. Also the identity function and constant functions are trivially continuous.

[Anonymous No.16112031]

How is it that if supX>b then there is an element x in X such that x>b?

[Anonymous No.16112033]

>>16112031
if there were no such x, then b would be the greatest element of X and would thus be the supremum itself

[Anonymous No.16112079]

>>16109209
What does it mean when a scatterplot stratifies?

[Anonymous No.16112081]

>>16112079
PIcture if you don't know what I'm talkinga bout.

[Anonymous No.16112263]

Why won't anyone sell me 10mg of niacin?

Why is the smallest dose of niacin i can find on amazon fucking 25 mg?

[Anonymous No.16112266]

>>16112033
>if there were no such x, then b would be the greatest element of X
actually it just means that b is *an* upper bound, not necessarily the least.

[Anonymous No.16112303]

Is there anything in space that doesn't spin?

Tidally locked bodies DO NOT count, because they still spin, they just spin at the same speed they orbit so it merely has the illusion of not spinning.
I mean TRULY doesn't spin, just sits in space facing one direction as it hurtles around the void.

[Anonymous No.16112306]

>>16112303
you cant define spin without a reference.
we cant even guess space itself doesnt spin because we cant see something outside of space to reference it to.
that might even be fucking dark energy, we dont fucking know.

[Anonymous No.16112310]

>>16112306
Thank you for pointing out why my question is very truly stupid.

[Anonymous No.16112330]

>>16112306
I am not sure that is true. Spin means a rotating reference frame, that means there is (rotational) acceleration. Acceleration is *not* relative. Even though we stand on the earth and move with it we can still measure the force produced by its spin. So theoretically you place a measuring device on some body and be able to tell if it was spinning or not.

[Anonymous No.16112334]

>>16112330
spin means having angular momentum, not rotating reference frame. One object moving straight forward past another object if they dont crash will have an angular momentum. Still is relative

[Anonymous No.16112371]

>>16112079
>>16112081
I'm not sure what you're looking for, but the variable on the y-axis is discrete (takes integer values).

[Anonymous No.16112373]

>>16112330
Do tidally locked planets still experience rotational acceleration as they travel around their star?

[Anonymous No.16112489]

Would laying insulated underground copper heat pipes between hot and cold regions of the US be an effective way to lower energy consumption related to air conditioning?

[Anonymous No.16112514]

>>16111124
Thank you so much anon <3

[Anonymous No.16112523]

>>16112489
subsurface soil temperatures are like 10c

[Anonymous No.16112591]

>>16112523
can that be used to cool a 40c house? like a giant heat sink underground that exchanges heat between surface air and subsurface soil?

[Anonymous No.16112599]

explain the truth of the races

[Anonymous No.16112607]

>>16111656
Just increases the air pressure in the room no?

[Anonymous No.16112679]

>>16112599
races are different paint jobs. what you should give a fuck about are the prevalence of human subspecies genes. we are all at least 1% neanderthal, including south africans. but not every human has denisovian dna. is it good? is it bad? i dont know, but i must point out to you, the hybrids won. there are no pure neanderthals left, no pure denisovians. theyre all dead. somehow the combination of them were far better than their constituent parts. so maybe purity isnt the answer.

[Anonymous No.16112686]

>>16109209
Imagine a train with 4 stops labeled 1,2,3,4 and a rider. The rider selects a number and begins his journey.

He must preserve the direction of travel and can only jump from 1 to 2, 2 to 3, 3 to 4, 4 to 3, 3 to 2, 2 to 1 and back to 1 to 2. Single jumps only. The number he selects represents the number of jumps he must make. He must preserve direction unless he wins up at a non-existent station 5 or 0, then he can change direction to go back to 1 or 3.

He runs this selected number for 8 loops, maintaining direction and station for each loop. If he visits each station at the end of each loop then return a True, otherwise if he can't visit a station given his selected number then return false.

Produces this pattern:
FTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFFFTFTFF


Returns True for all primes except 2 and 3.

Why does this pattern land on primes?

[Anonymous No.16112752]

>>16112679
so what your saying is we are one race but different subspecies but some subspecies are superior to others?

[Anonymous No.16112754]

>>16112752
im saying race is like phrenology. even if you want to be racist in principle, using race for it is dumb.

[Anonymous No.16112757]

>>16112686
I'm sure you think you have explained your problem clearly so we can understand it, but you really haven't.

[Anonymous No.16112759]

>>16112371
Doesn't a scatterplot that levels out like that mean that there is no correlation?

[Anonymous No.16112784]

>>16112757
That's why I put it in the stupid thread.

Does this visual clear things up?

[Anonymous No.16112823]

>>16112784
Not entirely. How is that supposed to produce prime numbers or any numbers at all? Don't post that pattern string, it's near impossible to interpret.

[Anonymous No.16112855]

Lets get AI to clear up my brainfog.

The Setting: There's a train line with four stations, numbered 1 through 4.
The Rider's Challenge: A rider picks a number that represents how many stations he'll move through in a specific direction during one "loop" or journey. He will repeat this journey 8 times in total.
Rules of Movement:
The rider moves from station 1 to 2, 2 to 3, 3 to 4, and then can go in reverse: 4 to 3, 3 to 2, 2 to 1.
The rider can only move one station at a time.
If the rider reaches station 4 and still needs to move forward based on his chosen number, he changes direction and goes back (e.g., from 4 to 3).
Similarly, if he's at station 1 and needs to move backward, he changes direction to move forward (from 1 to 2).
Winning Condition: The rider aims to end up at each of the four stations at the conclusion of each of the 8 loops. If he can do this at least once for each station, the result is True. If he misses any station, the result is False.

[Anonymous No.16112861]

>>16112823
Forgot to mention.

It doesn't produce prime numbers. The pattern just happens to be true for prime numbers except for 2 and 3.

It's true for some non-primes too, but primes will fall within the pattern.

[Anonymous No.16113362]

>>16112861
assuming I understand what the fuck you're talking about: Let's look at what actually happens with a jump of size 2.

We have two basic options: If we do not run into a wall halfway through, we change our position by 2. If we do run into a wall halfway through, then we change our position by 1, turn around, and undo it, so our position changes by 0.
So either we don't move, or we move by 2. But if we're on an odd space, that means we'll still be on an odd space, and likewise if we're on an even space then we'll still be on an even space. As a result, no matter how many tiles we have (unless it's only 1, in which case moving 2 spaces doesn't even make sense), you'll never be able to do it with a jump of size 2. In fact, you'll never be able to do it with ANY even-sized jump, since it will respect the even/odd parity.

3 is more specific to this case; our options are to either move 3 if we don't bounce off of a wall, or 1 if we do (2 in one direction, 1 in the other); in the latter case, we will never end adjacent to a wall. But if we start on 1 or 4, we will always be forced to move 3 spaces since there's nowhere else to move (we'd bounce off before even moving). Similarly, there's no way to get 3 spaces away from 2 or 3, so we're always going to have to bounce off of the wall and thus we'll end up on the other one of that pair. More generally, you will always find a failure if your number of moves and your number of tiles-1 share any common factors besides 1

[Anonymous No.16113376]

>>16112303
https://en.wikipedia.org/wiki/Bucket_argument

[Anonymous No.16113496]

What introductory book(s) would /sci/ recommend if I am interested on programming stuff like chess/poker/go solvers (or "simple" games in general). I asked ChatGPT and got the following list, but would like a second opinion:
1. **"Programming Game AI by Example" by Mat Buckland**

2. **"Artificial Intelligence: A Modern Approach" by Stuart Russell and Peter Norvig**

3. **"Deep Learning for Coders with Fastai and PyTorch: AI Applications Without a PhD" by Jeremy Howard and Sylvain Gugger**

4. **"Hands-On Reinforcement Learning with Python" by Sudharsan Ravichandiran**

5. **"Poker AI: The High-Stakes Game of Poker Applied to Business" by Aaron Davidson**

[Anonymous No.16113575]

>>16112759
I don't see why it should.

[Anonymous No.16113590]

>>16112784
You forgot the output condition. Which is true and which is false.

[Anonymous No.16113614]

>>16113575
So its leveling out like that because of a discrete value?

[Anonymous No.16113633]

I was trying to find the solution to e^x=1/x, but got a wrong answer, where did I go wrong?
f(x)=e^x-1/x=0
(xe^x-1)/x=0 -> xe^x-1=0, xe^x=1
xlnxe=0
lnxe=0, since x can't be 0
lnx +lne=0
lnx+1=0
lnx=-1
x=e^-1

[Anonymous No.16113699]

>>16113633
Your mistake was going from [math]xe^x=1[/math], to [math]x\ln{x}=0[/math].

[math]\ln(ab) = \ln{a} + \ln{b}[/math], so the correct step would be [math]\ln{x} + x=0[/math]. However going down this path is not going to give you the answer. You need to go read about the Lambert W function. The answer to you question would in this case be W(1).

[Anonymous No.16113855]

>>16113699
Without the lambert function how do I prove this function has only one real numbered solution?

[Anonymous No.16113907]

can a hole in a semiconductor cause impact ionization (avalanche)?

[Anonymous No.16113919]

>>16113496
Russell and Norvig is good but general, the classic for reinforcement learning is Sutton and Barto 2nd ed. Never heard of the other 3 (#5 is made up)
Beyond that, there are courses like David Silver's RL course (mostly equivalent to Sutton and Barto but has videos) and Csaba Szepesvári's course (super theoretical)
Other than that you will have to read papers and self-learn. For chess, there is also chessprogramming.org

There are two main cutting-edge approaches to solving this type of games: tree search with hardcoded heuristics (early Stockfish) and tree-search with learned heuristics (AlphaZero and other Deep RL approaches)
You can learn a lot about the first approach from chessprogramming.org. Deep RL requires some familiarity with neural networks (mostly MLPs and CNNs, transformer-based deep RL has only very recently been tried). There are lots of AlphaZero implementations around, I think this one is fairly minimal and didactic: https://github.com/fnclovers/Minimal-AlphaZero/tree/master while LightZero is the most general
Poker is absolutely not a simple game because of the randomness and hidden information. Making good poker bots requires a fair amount of game theory. The key algorithm here is Counterfactual Regret Minimization (minimal didactic impl.: https://justinsermeno.com/posts/cfr/))
Deep RL also works really well for single player games like video games (look up MuZero)

[Anonymous No.16113921]

>>16113496
>>16113919
forgot to mention this website which is also good: https://spinningup.openai.com/en/latest/index.html

[Anonymous No.16113932]

>>16113855
Can't you just graph it?

[Anonymous No.16113940]

>>16113855
for [math]x>0[/math], [math]f[/math] has a negative lower limit and a positive upper limit, so [math]f(x) = 0[/math] has at least one solution per the IVT
however [math]f[/math] is also strictly increasing in that interval ([math]f'(x) > 0[/math] for any [math]x > 0[/math]), so that solution is unique (since [math]f[/math] is injective)
for [math]x<0[/math], the function is positive so the equation has no negative-valued real solution

[Anonymous No.16113957]

>>16113855
[math]\displaystyle
\frac{d}{dx} \left( xe^x - 1 = 0 \right) = e^x + xe^x = e^x(1+x)
[/math]
[math]e^x(1+x)[/math] is clearly negative for x < -1 and positive for x > -1.
since [math] \displaystyle \lim_{x \to - \infty} xe^x - 1 = -1[/math], there are no solutions to less than -1, and since [math] \displaystyle \lim_{x \to \infty} xe^x - 1 = \infty[/math], there must be exactly one solution between -1 and +infinity.

[Anonymous No.16113983]

Why did the news instantly deboonk the possibility that the earthquakes could be connected to the eclipse when a quick search shows that the moon does in fact interfere with the sun’s gravity when it is in between the two of us and slightly decreases the gravitational force on the Earth from the sun?

[Anonymous No.16114308]

Can anyone explain what Sequentially Shifted Excitation actually is, cause everyone else just says it's a thing and I don't know what it actually does.

[Anonymous No.16114326]

>>16113983
The moon is between the earth and sun once a month, whether there's an eclipse has to do with the tilt in the Moon's orbit so the tidal forces for a regular new moon and eclipse are almost exactly the same
Also the Moon being on the same side as the Sun *increases* the gravitational force on the Sun-Moon-Earth axis and decreases it in perpendicular areas (this is how tides work and why they vary in a monthly cycle). Gravitational vectors are additive, no interference is possible
That said tidal forces *do* influence earthquake frequency and it's probably fair to say that they trigger earthquakes, but only for some types of faults, namely vertical faults (aka dip-slip or normal faults). The Ramapo fault is of this type so it's plausible that the phase of the moon contributed to the earthquake. The Moon was at its zenith when the earthquake occurred, which checks out with the theory. But the tidal force maximum happens twice every 24 hours. There's no mechanism for an additional effect related to the eclipse compared to a regular tidal maximum (the spring tide effect from the Moon and Sun being aligned is not that big)

[Anonymous No.16114489]

Fix some real numbers [math]a_1, a_2, \ldots, a_N \in \mathbb{R}[/math]. Consider also some weights [math]c_i \geq 0, i = 1, \ldots, N[/math], that sum to 1, [math]\sum_{i=1}^N c_i = 1[/math]. Define [math]f(c) = \left( \sum_{i=1}^N c_i a_i \right)^2[/math] as (the square of) the weighted average of [math]a[/math].

Now suppose I want to generalize to "weights" that can be negative. Call them [math]c_i' \in \mathbb{R}[/math]. We normalize them as follows: [math]\sum_{i=1}^N |c_i'| \leq 1[/math]. The set of all [math]c'[/math] is clearly a superset of all [math]c[/math]. My question is, for any [math]c'[/math], does there exist a [math]c[/math] such that [math]f(c') \leq f(c)[/math] (for any fixed [math]a[/math])?

[Anonymous No.16114701]

Photon questions:

Can a photon exchange be thought of as a charged particle choosing a random other charged particle within it's line of sight to exchange momentum with?

If the photon exists as a probability wave, does this wave just "flip a coin" as it passes over each particle it has the potential to interact with? Thus making close particles more likely choices than distant particles?

Is it possible that some photon emitted over the course of the universe have managed to avoid interacting with any particle around it, thus being stuck in superposition forever? Or will it always choose a particle? Does this make single particle universes impossible?

[Anonymous No.16114742]

how do I get a gf as an autistic math retard.
There are like 20 math majors in my senior class, most of them are actuary and education.
Like 5 people were in my real analysis class.
I haven't talked to any of these people in the 4 years I have been in math.
I'm starting to feel really sad because I was a loner nerd in hs because I like math and computers and now I'm somehow still a fucking loner loser retard autist. I mean I've already accepted at my ideal grad school and I'm going to go in as a fucking loner loser retard autist that never even hugged a girl before.
I mean one time an economics girl was kind of into me, but I didn't do anything because I'm a shy embarrassing idiot.
All the other true math guys seem to not care, they are all much better than me too. The only time we talked was indirectly in class trying to one up each other and they always win. I don't even know how I got into grad school, I'm bottom of the barrel. I just feel like giving up.

[Anonymous No.16114780]

>>16114742
Just own up to it the next time a girl gives you the opportunity. You will be fine.

[Anonymous No.16114795]

>>16114780
That will literally never happen again
it's probabilistically impossible

[Anonymous No.16114801]

anyone here who i can pay to do my discrete math hw? i have a packet of 15 questions that need to be done

[Anonymous No.16114802]

>>16114742
If you got into grad school, by definition you can't be bottom of the barrel.

> The only time we talked was indirectly in class trying to one up each other and they always win
If you're an admitted autist what did you expect? Using a game analogy you tried to compete with your weakest stat against their strongest. As for the rest even normies feel imposter syndrome. The only thing they are better at than you is hiding that fact.

[Anonymous No.16114809]

>>16114742
learn about enough things so that you can small talk with all types of people, then practice opening statements you can use on various people in your life until youre comfortable chatting everyone up

[Anonymous No.16114822]

>>16114802
>by definition you can't be bottom of the barrel.
Well you know what I mean, bottom of the barrel in my own barrel.
>If you're an admitted autist what did you expect?
Well some of them have girlfriends and I don't so it pisses me off that they're better than me all the time.
>>16114809
How an I supposed to know what to say to people? also talking for hours seems very tiresome

[Anonymous No.16115023]

Is a PHD needed to do a blog ? Almost every CS PHD I know has one website

[Anonymous No.16115099]

Is trachea literally a hollow pipe? Would sort of catching net that prevents foreign objects from entering but lets air in work?

[Anonymous No.16115201]

>>16115023
no but as a STEM PhD it's kind of expected that you have a website with your papers if not necessarily a blog

[Anonymous No.16115241]

How exactly does electrical capacitance work?

[Anonymous No.16115410]

>>16115241
most things can hold a certain amount of charge. If a person jumps and grabs onto a power line, charge flows in and the person will hold a small amount of charge. Let go and touch the ground or a piece of metal and u discharge that small amount.

[Anonymous No.16115565]

>>16115410
If you don't know then why answer?

[Anonymous No.16115573]

>>16115099
i think the reason we didn't evolve something like that is "overengineering", basically.
it would probably be fragile, and if it WERE damaged, it could cause persistent problems.
also, anything which makes breathing less efficient (even a little bit) is going to have a heavy evolutionary cost.

[Anonymous No.16115603]

finally done with my 370 page mechanics book

[Anonymous No.16115606]

>>16114742
impostor syndrome claims another victim

[Anonymous No.16115662]

>>16115603
Brutal I fucking hate physics, it's such fucking bullshit
I dunno, I wish they wrote physics books for mathematicians. I could read rudin no problem, but a physics book? I'd just close it never come back. They're usually unreadable trash.
The worst is that they are never able to offer either a meaningful physical explanation nor a mathematical one.

[Anonymous No.16115804]

>>16115662
> I wish they wrote physics books for mathematicians.
Say hi to your new favorite textbooks.

[Anonymous No.16115811]

>>16115804
nta but why am I salivating?

[Anonymous No.16115828]

>>16115804
>those covers
they know their target audience

[Anonymous No.16115869]

Is there a math symbol for the expression "implied to be equal"?
Like how "defined to be equal" is :=

[Anonymous No.16115923]

>>16115811
You're secretly a masochist? That series of books is highly regarded but also infamous for being mathematically challenging.

[Anonymous No.16115975]

>>16115804
Those are fucking hideous looking, but you know I'll thumb through them. At least it's not the physic book bullshit cover art with the fucking space or gears or globes like what the fuck.
I swear to god though if I see any bullshit jimmy and sally problems where jimmy throws and apple at a 30 degree angle I'm gonna beat them both to death with a fucking topological space.

[Anonymous No.16116040]

>>16115201
yeah that makes sense, was just noticing this behavior

[Anonymous No.16116066]

Griffiths Electrodynamics: why does it state that x runs from 0 to (1-y)? Should it not say x runs from 0 to 1, like with y?

[Anonymous No.16116104]

>>16115869
>Is there a math symbol for the expression "implied to be equal"?
that's just =

if you're thinking of something like manipulation of equalities
[math]A=B \implies A'=B'[/math]
then you can't do much better than this, since an infix symbol can't be used to represent a quaternary relation

[Anonymous No.16116105]

>>16116066
show me figure 1.24

[Anonymous No.16116122]

>>16116066
No, because not every combination of x and y is possible.
If you evaluated both from 0 to 1 without consideration of each other, that would include evaluating at, say, (1,1,z), which is obviously not contained within the prism. Since the boundary is the line x=1-y, that forms your upper bound.

If you integrated along y first, similarly, you'd have to have 1-x as your upper bound.

[Anonymous No.16116158]

I decided to get a hobby and make vidya games but it's been about 8 years since I last did calculus and I'm getting filtered pretty bad.
I don't know how much sense this picture makes, but I've got a function (on the left) that spits out a radian between -[math]\pi[/math] and [math]\pi[/math]. Unfortunately, that doesn't correspond with how the engine (on the right) uses those values.
I think I'm trying to ask how to translate the values on the left into the values on the right.

[Anonymous No.16116166]

>>16116158
Not sure what those blue values are meant to represent but the rest is just a reflection about the x axis. So g(x) = -(x + pi) and using the fact 2pi radians is the same as 0 radians.

[Anonymous No.16116178]

>>16116166
That should do the trick, thanks anon! I feel very dumb for missing it.

[Anonymous No.16116187]

>>16116178
Why did you post blank image?

[Anonymous No.16116207]

>>16116158
just rotate your values by 180 or [math]\pi[\math] degrees

[Anonymous No.16116225]

Any optometry chads here? What's my right prescription from pic related?

[Anonymous No.16116424]

>>16116066
>Griffiths Electrodynamics: why does it state that x runs from 0 to (1-y)? Should it not say x runs from 0 to 1, like with y?

One way of thinking about it:
- If you are integrating over anything more complicated than a line (one variable) square (two variables) or rectangle (three variables) you will need to define your integration limits as a function depending on other variable.
- When you integrate you need at least one dumb variable that you will simply move in an interval like in your case [0, 1] or [3,0]
- The other intervals will be determined by functions over other variables. In your case the interval of x is determined by 0 and a function of y.
- When you sequantially integrate over each variable you make each variable disappear making your expresion dependant on the variable that is easy to integrate.

In your example
- x depends on y moving in (0, 1-y)
- y moves in (0,1)
- z moves in (3,0)
So you integrate x before y. You could integrate y and z in any order you like

If you had something like
- x in (0, 1-y)
- y in (0,1)
- z in ( (1-x),0)

Your order of integration should be
z -> x -> y

[Anonymous No.16116527]

Does morality require sacrifice?

[Anonymous No.16116570]

>>16116527
No. It is not required.

[Anonymous No.16116623]

I've got an iteration on an existing mechanism in my head, but I'm not an engineer. If I hire one to do a CAD version of it, assuming it's possible, will the CAD be viable as an actual product, or is all of the movement and gadgets inside just for show?

[Anonymous No.16116807]

[eqn]\Phi_{g}(v_{\sigma^{-1}(1)}) \otimes \dotsm \otimes \Phi_{g}(v_{\sigma^{-1}(k)}) = \sigma \triangleright (\Phi_{g}(v_{1}) \otimes \dotsm \otimes \Phi_{g}(v_{k}))[/eqn]Would you say this is legitimate?

[Anonymous No.16116813]

In economics, what is a "learning curve"? Please help

[Anonymous No.16116936]

Why do crystals with central symmetry have zero quadratic susceptibility ([math]\chi^{(2)}[/math])? I keep reading it but I can't find an actual explanation. Do they also have zero [math]\chi^{(4)}[/math]?

[Anonymous No.16116959]

>>16116936
See picrel from the textbook by Boyd
All even susceptibilities are zero (you can see this in high harmonic generation experiments)

[Anonymous No.16117095]

"Prove that a matrix with coefficients in an algebraically closed field is similar to its transpose. Is this result true over [math]\mathbb{R}[/math]?"
I proved this exercise using the similarity to the Jordan form etc, that's not my point. About the last part of this exercise, I was tempted to say that, since [math]\mathbb{R}[/math] is not a closed field, a matrix with coefficients in [math]\mathbb{R}[/math] it's not similar to its transpose. But then I remembered another of the exercises that we had to prove:
"Suppose [math]A, B \in M_{n}(\mathbb{R})[/math] satisfy that there exists [math]C \in M_{n}(\mathbb{C})[/math] such that [math]A=C B C^{-1}[/math]. Prove that there exists [math]D \in M_{n}(\mathbb{R})[/math] such that [math]A=D B D^{-1}[/math].
Extra: Does the same result hold if we change [math]\mathbb{R}[/math] to [math]\mathbb{Q}[/math]?"
And since I was able to prove this one, does that mean that even if [math]\mathbb{R}[/math] is not a closed field, every matrix with coefficients in [math]\mathbb{R}[/math] does admit a JCF?

[Anonymous No.16117194]

>>16116959
Oh that was quite simple. Thanks.
Is it at all important that the electric field oscillatese as [math]\cos{\omega t}[/math]? It doesn't seem like the proof makes use of this.

[Anonymous No.16117201]

If there are aliens thousands of light years away how do we reach them?

[Anonymous No.16117246]

>>16117194
I'm not completely sure but I think it shouldn't matter

[Anonymous No.16117346]

>>16117201
If you can build an engine that accelerates at a comfortable 9.81m/s^2 you can reach them in 20 years, if they're near the center of the galaxy and in about 3 years if they're in our immediate vicinity.

[Anonymous No.16117634]

>>16109209
Is Propylene carbonate stable in water at a pH of 8.5 ?

[Anonymous No.16117671]

>>16117634
It's used as a solvent so it's probably very stable. I don't see why it will not by stable at that pH.

[Anonymous No.16117677]

>>16117671
Its still able to do hydrolysis, but i wonder if its slow enouth to be stored for years

[Anonymous No.16117682]

>>16110317
You're applying a continuous function (on the particular domain) to both sides of an equation. Because both sides are equal, the result of the function will be equal. x = y implies f(x) = f(y)

Most of the time it's really simple, like f(t) = t + 2

5 = x - 2
f(5) = f(x - 2)
5 + 2 = x - 2 + 2
7 = x

[Anonymous No.16117683]

fags

[Anonymous No.16117828]

>>16109209
what is the gene for laziness/high-time-preference/procrastination? I know it's generally associated with melanin, and whites and asians generally are pretty productive, but what is the actual gene or set of genes? I'm white and black and I feel like my blackness often inhibits my white ingenuity.

[Anonymous No.16117832]

>>16117828
The body doesn't work like that. It is a complex, disparate, web of interlocking systems. There is rarely, if ever, a single gene for anything.

[Anonymous No.16117839]

What that solar eclipse start time and duration mean? The time when the moon starts to overlap the sun or it is the start and duration of the total eclipse and the sun will be totally eclipsed for 3 minutes? If the latter then how do I know when the moon starts blocking the sun, so the sun would look like a crescent until it is completely eclipsed? Would it take like an hour or so?

[Anonymous No.16117855]

>>16117839
Start and stop times are typically given from when the obscuration begins until the transit is fully over, so that will be hours long. Duration is how long the sun will be fully covered and that will be several minutes.

[Anonymous No.16118277]

>>16117828
personality traits are influenced by hundreds of genes and some of the genes might have a tradeoff where it makes you lazier but also healthier or some other benefit

[germiphobe No.16118307]

>>16109209
which evaporates faster, 70% ethanol or 90% isopropyl?
Also, what happens if I mix acetone with either ingredient? I want to make my own homemade hand sanitizer, a mix between fast orange type solvent degreaser and regular germ killing alcohol based hand sanitizer. Acetone is the only off the shelf solvent that I can think of adding. I'll skip the pumice powder.
This is what I currently do. I use hand sanitizer to kill the germs, and then I used a solvent(pic related) to dissolve the oils on my hand, then I use a paper towel to wipe my hands dry. There's nothing I hate more than getting someone else's grease on me. Like touching a greasy doorknob or shaking a man's hand. I heard that oily substances are the number one way that germs are able to stick to your hand.

[Anonymous No.16118317]

if you were instantly placed in the very center of a room that had a pressure equivalent to the bottom of the mariana trench (or any excessively high pressure), how would the body be compressed? does it depend on the pressure's directionality?
for example, if you were at the bottom of the ocean for real, i would assume the vast majority of the pressure bears down and then in relative to the body, so you would probably turn into a seafloor pancake
if by some happenstance the pressure converges at the spatial center of the room, are you just turned into a ball of paste that sits at that center?
is there any way to construct a situation in which the body basically gets turned into a stick figure before becoming a ball/pancake, or would that require varied pressure across the space?
i mostly came to wonder this because i was writing something and don't know what order the body would compress in. like, would the extremities shrivel first, or would the body just collapse in the direction of the force, etc
i promise i'm not a psychopath

[Anonymous No.16118452]

Is Khan Academy any good? Any other good educational platforms, preferably not too expensive?

[Anonymous No.16118576]

>>16110801
Our bodies are better adapted to processing saturated and monounsaturated fats due to to evolutionary exposure in the wild. You want to avoid poly and trans fats as those are shown to be linked with high risk of various health diseases, heart included. Research is coming out indicating that our bodies are better adapted to consuming saturated fats above all others and further evidence points to a lower risk of heart disease when consuming saturated fats as opposed to others, monounsaturated fats aside. The research that points to either saturated or monounsaturated fats causing heart disease is dubious at best and, go figure, typically funded by seed oil companies looking to peddle "vegetable" oil trash.

Basically, if you're cooking or just eating in general, avoid pre-processed or fast food goyslop, and eat butter (low heat), clarified butter (high heat), olive oil (low heat), or avocado oil (high heat) to you heart's desire.

[Anonymous No.16118609]

>>16118452
MIT opencourseware

[Anonymous No.16118671]

>>16117839

[Anonymous No.16118988]

>>16118452
Khan Academy is very good if you want to start from the absolute basics and improve your knowledge at your own pace, and they cover all the topics you would get taught at school. It's downside is that it is very focused on the US curriculum. But hey, its 100% free, that's a small inconvenience for most people.

>>16118609
MIT is good too, they just tend to cover slightly more advanced topics.

[Anonymous No.16119582]

https://en.wikipedia.org/wiki/Lidocaine#Interactions
>Any drugs that are also ligands of CYP3A4 and CYP1A2 can potentially increase serum levels and potential for toxicity or decrease serum levels and the efficacy, depending on whether they induce or inhibit the enzymes, respectively.
https://pubmed.ncbi.nlm.nih.gov/16918719/
>We conclude that inhibition of CYP1A2 by fluvoxamine considerably reduces the presystemic metabolism of oral lidocaine and may increase the risk of lidocaine toxicity if lidocaine is ingested.
is wikipedia wrong here or what? if i read it right, it's saying fluvoxamine should decrease serum levels and efficacy since it's an inhibitor of those two enzymes

[Anonymous No.16119808]

>>16118609
>>16118988
Thanks. I'm a literal autist and getting back to math and scientific subjects after becoming rusty.

[Anonymous No.16119913]

why so many /sci/ fags hate astronomy and stargazers?

[Anonymous No.16119992]

>>16109209
Can a very strong magnetic field be used to control chemical reactions to create new chemicals that would otherwise to occure? I read/heard where MRIs can align and release the electrons in your body at high frequencies to create an image, and I was curious if this affects the chemistry.

[Anonymous No.16119994]

>>16118452
>any good?
for what? What are you looking to do?

[Anonymous No.16119997]

What are some good supplement brands? I'm looking at "NOW" brand, but some redditor claims they source from china.

[Anonymous No.16120002]

>>16119913
You're on 4ch, there are people who hates everything.

[Anonymous No.16120067]

Can the solar eclipse be partial for every observer on the earth? Or there gotta be a spot where it is total?

[Anonymous No.16120070]

>>16120067
Most solar eclipses never achieve totality anywhere on Earth. Totality is achieved when the viewer is in the darkest part of the moon's shadow, called the umbra. But the moon moves up and down as it orbits Earth, so if the umbra is cast beyond the poles, none of it intersects Earth, and as a result even if several people are able to see a partial eclipse nobody is able to see totality

[Anonymous No.16120338]

Some politics eceleb streamer guy had a mental breakdown and started obsessing over physics despite having no background in it. Can someone tell me if there is any validity to this whatsoever or is it pure schizo shit like I assume?
https://www.tiktok.com/@observerphysics/video/7354026561814809902

[Anonymous No.16120341]

If you could travel at the speed of light (or infinitely close to it) on earths surface with an indestructible body, what would be some of the most extreme effects on the environment? What temperature would you get up to? Would you create nuke-like explosions everwhere you went? etc etc

[Anonymous No.16120353]

Would it be a waste of time for me, to practice "basic math" such as arithmetic, algebra or trigonometry, if these did slow me down on exams on classes such as calculus, physics or ordinary differential equations ?

[Anonymous No.16120362]

>>16120353
Are you actually in those classes now? In my experience most professors either let you use a calculator or let you leave the arithmetic unsimplified.
Trigonometry yeah though you should at least know how to quickly use the basic functions and their inverses to find an angle or a side

[Anonymous No.16120492]

>>16118307
someone answer this question

[Anonymous No.16120494]

>>16120341
A massive body cannot travel at the speed of light or infinitely close to it, but this is what would happen if you traveled close to it: https://what-if.xkcd.com/1/

[Anonymous No.16120616]

>>16120362
Nope, actually passed the courses.
Yet these topics might be important later if I plan to do either a masters or PhD, for advanced calculus courses or similar topics. (I'm an engineering student)

[Anonymous No.16120914]

If f(x)>=0 for all x in (a-delta,a) then how do I know that lim(x->a-) f(x)>=0 ? Is there some kind of proof for this kind of thing?

[Anonymous No.16121042]

let f:R->R be differentiable 4 times, where f'(a=f''(a)=f'''(a)=0 and f''''(a)>0, how do I prove with Taylor series that f has a local minimum in a?

[Anonymous No.16121135]

Anyone else's social anxiety ruin every meeting you have with a person

[Anonymous No.16121324]

>>16121135
Learn to breath. Learn to disassociate a bit. Learn to play a character. Approaching every conversation in a goal oriented manner has also helped me in the past, at least to get over the worst of the anxiety.

How bad is it?

[Anonymous No.16121347]

>>16121324
Very bad. Its like I become a complete retard when talking to people

[Anonymous No.16121351]

>>16121042
consider a very small [math]h[/math] such as [math]f^{(4)}(a+h) > 0[/math]
then by Taylor's theorem
[eqn]f(a+h)=\sum_{k=0}^4 \frac{f^{(k)}(a)}{k!}h^k = f(a) + \frac{f^{(4)}(a)}{24}h^4[/eqn]
hence [math]f(a+h) > f(a)[/math], so [math]a[/math] is a local minimum

[Anonymous No.16121857]

Does any of this have any practical application, or at the very least theoretical application

[Anonymous No.16121900]

>>16121857
If you are talking about that image, none at all. It is just another example of the strong law of small numbers. Which paraphrased essentially amounts to you can assign as many seemingly magical relationships and properties between numbers as you can think of when those numbers are small, but when you use larger numbers all that nonsense just disappears.

If you are talking about number theory in general, absolutely. Modern encryption for one.

[Anonymous No.16121964]

Do feminists get orgasms?
I could understand being an awful bitch and hating the opposite sex if you've never cum before

[Anonymous No.16121972]

>>16121964
I would answer that you should perform an experiment but since you have never made a woman cum you can't have a control group.

[Anonymous No.16122280]

I have to show that a linear map [math]\phi: U \to U'[/math] induces another linear map [eqn]\phi^*: \text{Hom}(U,\, \text{Hom}(V,\, W)) \to \text{Hom}(U', \text{Hom}(V, W)).[/eqn] There's no further context, so I'm not sure what I'm supposed to do here. At first I thought I only had to point out that this is the pull-back with [math]\phi[/math]. Sadly U and U' are in the wrong positions. Do you know what they want me to do here?

[Anonymous No.16122617]

>>16121964
funny, i find the more i orgasm the more i hate women.

[Anonymous No.16122854]

>>16120914
do a proof by contradiction, like assume it's less than 0, then use the limit definition to contradict the initial statement

[Anonymous No.16123065]

Sup. Anyone knows the solution to a differential equation [math] x'' x^2 = 1[/math] ?
There's a hint to multiply it by x' but I can't figure it out anyways. Probably trivial, I'm just stuck on this one.

[Anonymous No.16123098]

>>16123065
for y'' = y^a where a is constant, set y = x^n, for some unknown n. See if u get anything

[Anonymous No.16123101]

[Anonymous No.16123114]

there always is some context. what document does this come from?
if its introductory material, I assume there is a typo and the induced map is nothing but precomposition with [math]\phi[/math].

if its not introductory, then there is likely something going on which you can find in theory that came before, that lets you construct such a linear map.

[Anonymous No.16123116]

>>16123114
was ment for >>16122280

[Anonymous No.16123270]

bros i need help, official exercise solution says its 15/2 but the result i get is always 15/11

[Anonymous No.16123366]

>>16123270
The answer is (15 / 2) / 11, so 15/22. It could just be a simply typo in the answer.

[Anonymous No.16123494]

>>16117095
no because
0 -1
1 0
has eigenvalues i, so no JCF over R only over C. But it is similar to all matrices with eigenvalues i, -i by your proof
look up frobenius normal form
>>16121351
application of Taylor's theorem should be a' in right side, and you choose h so that f^(4)(x)>0 for all x in (a-h,a+h).
Also, this argument needs that the fourth derivative is continuous
>>16123065
x''x'=x'/x^2
(x')^2/2=-1/x+C (integration)
now sqrt and separate variables

[Anonymous No.16123498]

are PIs in Asia racist ?
t.latino

[Anonymous No.16123534]

Is negative correlation as valid as positive correlation in prediction? Just say in a dataset a pearson correlation function returns -1 for a condition, should it be treated with same sincerity as a pearson event that returns 1?

[Anonymous No.16123581]

>>16123101
Need help with this one bros

[Anonymous No.16123764]

>>16123534
Yes because you can linearly transform one of your variables to get a positive correlation

[Anonymous No.16124019]

>>16123114
It's part (b) of an exercise from a linear algebra 2 book. The chapter was about tensor products. Here's part (a) of the exercise, which I worked out a solution for. Must be a typo, right?

[Anonymous No.16124076]

>>16123366
thanks bro thats what i was thinking i did the exercise over and over and there was no way it could be 15/2 i was going insane kek i did get 15/22 once or twice now i know what i need to improve thanks bro

[Anonymous No.16124123]

Here's an easier version of the problem. Take a_{i+1}=2 a_i for all i, except the last one. For instance 1, 2, 4, 8, 11. The last number is equal to 2^{n-1}-1-2x, where x is some nonnegative integer (possibly 0) strictly less than 2^{n-3}. In the example above, n=5, x=2

[math] \sum_{i=1}^{n-1} a_i =\sum_{i=1}^{n-1} 2^{i-1} = 2^{n-1}-1 = a_n + 2x [/math]
So to split it into two equal halves all we have to do is remove x from the sum and group it with a_n.

So can we construct any integer x < 2^{n-3} out of sums of powers of two from 1 up to 2^{n-4}? We can prove this inductively. Suppose we can construct any y < 2^{n-4} out of sums of powers of two from 1 up to 2^{n-5}. Now let 2^{n-4}<= x < 2^{n-3}. x-2^{n-4} < 2^{n-4} so we can construct it by the inductive assumption.

This completes the proof of the easier problem. If I have time today I might come back and think about the full thing.

[Anonymous No.16124128]

Oops, forgot to link the reply above
>>16123581
>>16123101

[Anonymous No.16124284]

>>16112686
It's not really about primes. First of all, notice that only numbers 0 through 5 actually matter and the pattern repeats after that. This is because 6 jumps takes you from 1 to 4 and all the way back and therefore is equivalent to 0 jumps. So let's consider the numbers 0 through 5 and see why some work and some don't. We could just as easily (and maybe less confusingly) view this as going from 1 to 6 and wrapping back around itself rather than worry about this ride orientation preserving stuff, so let's do that. i.e. now we're only moving forward, from 1 to 6 and then 6 wraps back around to 1. We can immediately see that all the same results as before will apply for numbers 0 through 6.

I'll give you two ways of analyzing this. One is more intuitive, and one is using some ideas from group theory. Really the two are equivalent, and I'm sure there are other perspectives you could find as well.

First, notice that an even number can't possibly work. Starting from station 1, with an even number of jumps we'll miss every odd station no matter how many times we go around. So do all the odd numbers work? Well, if we choose 3, that takes us from 1 to 4 to 7 (which is 1+6, and therefore 1). 4 is even so that can't work. What about 5? (I claim that 5 is actually equivalent to 1). 5 takes us from 1 to 6, then 5, then 4, then 3, then 2, so we visit all stations. Notice that 8 loops with the same number is actually excessive. So what do 1 and 5 have in common? They're both coprime with 6 (i.e. their greatest common divisor with 6 is 1). What about 0,2,3,4? Well we might as well consider 0 to be 6 because 0 jumps and 6 jumps are equivalent. Then these are all numbers which share prime factors with 6, i.e. they're not coprime.

That was an exhaustive approach but hopefully you can see the pattern. For a more formal approach, this question is equivalent to asking: what are the generators of the additive cyclic group Z_6. I leave it to you to find the connection.

[Anonymous No.16124316]

>>16114489
Not if we allow a_i to take both positive and negative values. I can provide a proof if you want but this should be fairly easy to see.

[Anonymous No.16124381]

How can this equation be used when the units are wrong? Magnetic field is Tesla, susceptibility is unitless, and magnetic dipole is A/m^2. I don't understand why this equation is so widely accepted when it is blatantly wrong. What am I missing?

[Anonymous No.16124399]

What kind of chart do I need or how would I format my data to get a chart like this? I want a percentage range inside a percentage scale.

For example one segment to show from 10% do 30%, the next one 20% to 60%, the third one 5% to 20%, etc.

[Anonymous No.16124464]

Is anyone familiar with this book?

[Anonymous No.16124465]

What does he mean by Time 2, is he just using it to measure duration?

>>16124464

[Anonymous No.16124582]

>>16124316
Ah gotcha, if there are differently signed a_i then the c_i' can conspire to match the signs, whereas the normal weights can at best zero out, say, the negatively signed a_i. Thanks.

[Anonymous No.16124627]

>>16124381
convolution is an integral

[Anonymous No.16124633]

>>16124399
if you're cluttering a single axis, that's bad. If you're talking about a range plot, thats fine.

[Anonymous No.16124831]

>>16115603
I'm 282 pages in of this 550 pages mechanics book. I'm so glad I focused heavily on mathematics this past year. It makes it child play at times.
Keep on, anon! We're gonna make it!

[Anonymous No.16124843]

>>16115975
No, desu. Jimmy trew it at 45 degree angle in an acclerating train, we want to know the maximun range in these conditions.

p.s. g = 10

[Anonymous No.16124855]

Im working on a question on condensed matter physics/solid state physics and I could really use some help.

General gist of the problem:
Have simple metal like sodium where each atom has 1 valence electron, and the electrons roam freely like particles in a box. The energy of the system is described by [math]r_s[/math] (which is the average distance between 2 valence electrons) using
[math]U(r_s)= \frac{\alpha}{r_s^2} - \frac{\beta}{r_s}[/math]

There are 2 parts to the question, the first says to assume the interatomic radius [math]R[/math] is equal to [math]r_s[/math], and to solve for the equilibrium value of [math]R[/math] in terms of [math] \alpha[/math] and [math] \beta [/math]. I'm pretty sure I have this part down.

The second part of the question is where I'm stuck. It asks to show that the system obeys the Virial theorem for electronic systems
[math]U(R_{min}) = -KE(R_{min})[/math]

The textbook doesn't mention the Virial theorem and I don't think it's been mentioned in class, so I'm fairly confident that an understanding of it isn't actually important, and that what the question is really trying to get me to do is calculate the kinetic energy of the electrons(?) or something along those lines.

We can look up the actual value of [math] R_0 [/math] for sodium in a table. Also, the problem says that the first term in the [math] U(r_s) [/math] is due to electronic kinetic energy, and the other term is a binding energy from the net Coulomb interaction between all charges. (there's a bit more, but I think its fluff so I'll leave it out for now)


>>TLDR: given a system of many sodium atoms where the energy of the system is [math]U(r_s)= \frac{\alpha}{r_s^2} - \frac{\beta}{r_s}[/math], how do I show that said system obeys the Virial theorem for electronic systems [math]U(R_{min}) = -KE(R_{min})[/math]?

[Anonymous No.16124860]

>>16110633
>>16110641
My electricity and magnetism class used that textbook, I think it was pretty good.

>am I getting filtered
No, electromagnetism is just really fucking hard, especially if you don't have a really strong grasp on calc 3 topics, ie multi-variable vector calculus. I very nearly got crucified in that class. Also the instructor makes a big difference. The professor I had was a terrible teacher and also just an asshole/terrible human being.

[Anonymous No.16124866]

>>16110835
>Calories in, calories out.
This is absolutely not true. Your body in some cases uses different metabolic pathways to process different yet similar compounds. The example I've heard about is fructose vs. glucose. The way your body processes fructose is apparently like 1 or 2 steps away from the way it processes alcohol, and is very different than the way it does glucose.

Yes, you can eat almost anything, but that doesn't mean everything you *can* eat is equal.

Even *when* you eat can make a difference. When you're asleep you mostly run on fat reserves after the stuff you last ate is no longer available, so when you wake up with no food in your stomach your body will continue to run on stored calories because there isn't any other choice until you eat something, at which point it will switch over to using "fresh" calories from your recently eaten food. A bit of light exercise before eating means your body will still be running on stored fat when its burning those calories.

[Anonymous No.16124878]

>>16118576
>You want to avoid poly and trans fats
trans fats have actually been illegal in the USA for food intended for humans for at least several years now. Not sure when it was, but at some point the FDA deemed it "unsafe for human consumption" and gave everyone x amount of time to come into compliance. It still has to be listed on nutrition information labels though as a formality or something. Thats why in the US at least the nutrition info label always lists trans fats on it and it always says 0.

My professor in my freshman health/gym class claimed that its only a single chemical step away from being some kind of plastic.(I realize that lots of things are only a few chemical steps from being a lot of other things, but I always remembered that and thought it was funny)

[Anonymous No.16124932]

>>16124878
>claimed that its only a single chemical step away from being some kind of plastic.
he's a moron. "muh chemicals" is a blatant scare tactic.
all trans- fats do is flip around the double bond of a cis- fat. their health hazards weren't immediately obvious.

[Anonymous No.16124967]

I asked ChatGPT to write a story about a superhero who rescues a boy from drowning but an ordinary citizen takes the credit for himself.

So it wrote a story about a superhero who rescues a boy and pulls him to shore in front of a crowd of people, then a man named Miguel arrives and tells the crowd that it's her fault the boy drowned and everyone cheers so Miguel becomes the hero of the city for rescuing the boy.

The fuck? Why is this program so stupid? How long before it's ready?

[Anonymous No.16124970]

>>16124967
Because ChatGPT is AI, not AGI. It's dumb as bricks. It has no understanding of what you ask or what it writes. Under the hood it is all just statistics.

As for when we have some form of AGI it could be 2 years, 20, or 200. Depends on who you ask.

[Anonymous No.16124982]

I have to review some basic electrical work hand outs from one of my previous classes. I don't work with electrical so this is pretty foreign to me. I'm trying to calculate the total resistance for a parallel circuit. The voltage is 120. The resistors are 58ohms in total. I calculate 120/58, which gives me 2.068ohms. My answer key and pic related say 2.20ohms. Where is the discrepancy and how do I arrive at the correct answer?

[Anonymous No.16125014]

>>16124855
idk man

Multi-part problems are often written so that the initial part of the problem helps you with the next part of the problem. Maybe use that.

Look up virial theorem if you dont know it. It's something similar to 2KE = nU. Figure out why n is important for virial theorem. In this case n is ___. It seems one of the terms is more important, idk.

[Anonymous No.16125017]

>>16124982
You took the voltage, divided it by ohms, and think that your answer is in ohms? Why are you even thinking about dividing 120 VOLTS by 58 OHMS? You cant just throw numbers randomly together.
There's literally a formula in ur picture. Have u tried using it?

[Anonymous No.16125039]

>>16124627
OK, so I have units of either T or A/m for the LHS for the magnetic field (impossible to know if they mean one or the other), and the units on the right are [Am^2][m^3], magnetic dipole times volume, since the convolution is a volume integral. The units still don't match. Where did I fuck up?

[Anonymous No.16125046]

>>16125017
It's because our handouts don't use the fancy formula. We never delved into anything that complicated (from what I recall). I remember the instructor having a simple way of calculating it. Sadly that was 4 years ago.

[Anonymous No.16125064]

>>16124381
>>16124627
>>16125039
From the original paper it can be deduced that the magnetic field is in Tesla, then they give two units for d (by showing the equations in the pic), A/m^4 and 1/m^3, the units for the equation with the convolution then gives T = A/m or T = unitless. It makes no sense. What am I missing?
m is a magnetization, so it must be in A/m.

[Anonymous No.16125072]

>>16124932
>their health hazards weren't immediately obvious.
Oh I'm not saying it was immediately obvious like from the time they first started showing up in food. Just that at some point research was done that showed that it was actually pretty bad for you, and has since been removed from all the food.

And like I said, I realize that there are many food molecules or other chemicals that are only a few small changes away from being something totally different. It's not something that bothers me; fact I revel in it. If you haven't heard of a youtube channel called "NileRed" you should look him up. He does (among other chemistry things) videos where he takes some chemical from something and turns it into other shit. His most recent one was converting styrofoam cups into a cinnamon flavor.

[Anonymous No.16125091]

>>16125064
there is a B_0 constant in the denominator. What unit do you think this is? So what should b(r) units be then?

[Anonymous No.16125712]

>>16124855
>Also, the problem says that the first term in the U(rs) is due to electronic kinetic energy, and the other term is a binding energy from the net Coulomb interaction between all charges

So write U like this
U(r_s) = KE(r_s)+PE(r_s)
U'(r_s) = (-2 KE(r_s) - PE(r_s) / r_s
In equilibrium U'(r_s) = 0, so PE = -2KE
That is exactly the virial theorem for a 1/r potential, so you're done

[Anonymous No.16125723]

Where can I stir up norms? I.e. put a point forward if I know shit from my personal exploration that's anecdotal to everyone who wasn't there?

[Anonymous No.16125726]

Does anyone have a proof of conservation of étendue for non-specular (e.g. Lambertian) reflections? It seems like all of the nice geometric ray optics proofs fall apart without perfectly reflective or refractive interactions.

[Anonymous No.16125755]

>>16121351
Why isn't the Lagrange remainder here? Also is there a simpler way to do it just by definiton? I get that f(x) =f(a)+(f''''(a)*(x-1)^4)/4!+ Rn(x), where the f''''(a)... part is positive, can I do something with this? I know I'm supposed to find a delta such that when x in (a-d,a+d) then f(x)>=f(a), but how exactly do I find this delta?

[Anonymous No.16125778]

I have a unbounded from below sequence and I want to construct a subsequence with a limit of -inf, apparently this proof is wrong, but I don't exactly get why: let n1=1
then we can find n_{2} such that x_{n_{2}}<-2, otherwise -2 would be a lower bound, analogously we can find an index n_{3} such that x_{n_{3}}<-3, otherwise -3 would be a lower bound etc, then it is obvious that the limit of such a subsequence is -infinity.
My teacher said something the lines of how do we know that n2<n3 or something like that

[Anonymous No.16125806]

I see you.

Yeah you, Grumpy.

[Anonymous No.16125858]

What is that [math]H_m^i[/math] referring to?

[Anonymous No.16125881]

>>16125858
Disregard this question, I figured it out.

[Anonymous No.16125919]

[eqn]\lim_{n\, \to\, \infty} \sum_{k = n}^\infty 1[/eqn]This limit diverges, right?

[Anonymous No.16125929]

>>16125778
Have you proven that the sets [math] \left \{ x_i \mid x_i < k \; \land i \geq n_{k-1}\right \} [/math] are all non-empty?

It's not enough to show that the sets [math] \left \{ x_i \mid x_i < k \right \} [/math] are non-empty.

[Anonymous No.16125934]

>>16125919
[eqn] \sum_{k=n}^\infty = \zeta(0) [/eqn]
So
[eqn] \lim_{n \to \infty} \sum_{k=n}^\infty = \lim_{n \to \infty} \zeta(0) = \zeta(0) = - \frac{1}{2} [/eqn]

[Anonymous No.16125940]

>>16125934
This can't be correct, because you could also prove that the constant 1-series converges that way. We're only supposed to use the epsilon-criterion for the convergence. If you go by that, the expression in >>16125919 should be divergent, right?

[Anonymous No.16125947]

It microwaves toxoplasmosis cat poo and eats the inactivated toxoplasmosis for its white blood cells

[Anonymous No.16125948]

>>16125726
Hello. Sorry for the delay. I was summoned here
You need to eat the cat poo

[Anonymous No.16125982]

Why don't we have more than one type of zero, I can think of 10-15 different zeros..

[Anonymous No.16125996]

https://blog.myrank.co.in/sum-of-sines-or-cosines-of-n-angles-in-a-p/
I was looking into the formula for the sum of sines of angles in ap.
by multiplying and dividing by cos (beta/2) instead of sin(beta/2) in the series, I got the final result to be :

[math]\frac{\sin \frac{n\beta }{2}}{\cos \frac{\beta }{2}}\times \cos \left( \alpha +\left( n-1 \right)\frac{\beta }{2} \right)[/math]

is it correct??

[Anonymous No.16125998]

>>16125948
>>16125726
Hello. Sorry for the delay. I was summoned here
You need to eat the cat poo

[Anonymous No.16126069]

>>16114489
Anon was wrong, you absolutely can. With fixed a, f attains its maximum on the subset of positive, sum-1 weights:
Choose the component of a with largest absolute value: [math]|a_k| = \max_i |a_i|[/math], and take [math]c_i = \delta_{ik}[/math] (1 in the k'th component, zero otherwise).
Now take any c':
[math]\sqrt{f(c')} = |\sum_i a_i c_i'| \le \sum_i |a_i| |c_i'| \le |a_k| \sum_i |c_i'| \le |a_k| = \sqrt{f(c)}.[/math]

[Anonymous No.16126190]

Assuming R = 5 m, is `DE = diff(phi, t, 2) + ((9.8/5) * sin(phi))` the proper way to convert this to Sage math?

[Anonymous No.16126197]

This might be more of a /g/ problem, but I don't know what I'm doing wrong.

[Anonymous No.16126199]

>>16126190
Usually, you'd just do it for small angles phi (range of 20 degrees of displacement of the pendulum) and approximate sin phi with phi. The values of g and R are not important for this. If you need a solution for bigger angles, you'll have to use numeric methods, because this DEQ is not analytically solvable.

[Anonymous No.16126206]

>electricity is transported at high voltage to minimize losses
>energy dissipation in a resistor is proportional to the voltage squared ([math]P=U^2/R[/math])
am I missing something or just retarded?

[Anonymous No.16126208]

>>16126199
I'm completely aware of that, the question is when I try to do it that way in sagemath I get the results seen in >>16126197

[Anonymous No.16126266]

Do you guys know if AHCC is actually a helpful supplement to take or is it fake and gay?

[Anonymous No.16126289]

>>16126206
https://physics.stackexchange.com/questions/248229
There are 2 different voltages involved, source voltage [math]V_S[/math] and the voltage drop [math]V_L[/math] in the transmission line, with the consumer getting [math]V_C = V_S - V_L[/math].
Transmission loss scales with [math]P_{loss} = V_L^2/R = I^2R[/math], but at the source you can only control [math]V_S[/math] and the current [math]I[/math], subject to the constraint that [math]V_SI = P_{in}[/math] is the power your power plant generates
Since you cannot control [math]V_L[/math] you instead bring down [math]I[/math] and max out [math]V_S[/math]. The disadvantage is you have to install transformers everywhere

[Anonymous No.16126367]

>>16112686
I was going to suggest this. This anon got it.

>>16112686
It's not giving true for all primes, they only appear prime-like to the untrained eye. It's giving T for all composites not containing 2 or 3 in their prime factorisation. That's why we see a T at spots 25, 35, 55, 49, 77, 91, etc...

I don't understand why it's necessary to do it 8 times, 6 is sufficient. You're essentially asking if you can generate all of {1,2,3,4} by cycling through them with steps of length 'n', but it's not the typical modular arithmetic. The total length of the path from 1 to 4 to 1 is 6 steps (1-2-3-4-3-2-1, count the hyphens). Any jump of length 2 will not generate all values (it only generates 1 and 3), thus any multiples of 2 can generate at most 1s and 3s. Likewise, any jump of length 3 cannot generate all values (it only produces 1s and 4s) so multiples of 3 can generate at most 1s and 4s. (in fact, multiples of both 2 and 3 only generate 1s, powers of 2 will generate 1s and 3s, powers of 3 will generate 1s and 4s).

Therefore, if it returns TRUE, then n is coprime with 6. In fact, the converse is also true but I haven't got a very good proof for that, all I can say is "well it kinda has to be true because only multiples of 2 and 3 will consistently skip values". This is similar to a very popular result in number theory, something to do with cyclic subgroups of Zn. It's not exactly the same scenario because in your example we turn back around once we reach 4.

If you made it 5 train stations then only powers of 2 would return false, 6 train stations and powers of 2 and 5 would give false, and in general if there are n train stations, then all multiples of 2 and n-1 will give false. You would have to repeat it 2n-2 times to ensure all elements can be generated.

[Anonymous No.16126377]

>>16126367
Oops, was meant to say this anon >>16126069 gets it

[Anonymous No.16126383]

>>16126208
It is a 2nd order diff equation and the error seems to be about the initial conditions which makes sense. You only gave it 1. You would have to specify the initial values for phi, t and dphi/dt

[Anonymous No.16126585]

>>16126383
What you said is true, and I did add those, but nothing has changed. Should I replace `phi` with t?

[Anonymous No.16126614]

>>16125017
Ah, it's the inverse button on the calculator. I'd forgotten all about that.
>Why are you even thinking about dividing 120 VOLTS by 58 OHMS?
It's all I had left over from my hand-out from five years ago and I didn't have the time to prod it more thoroughly. I was trying to reverse engineer it. Obviously incorrectly.

[Anonymous No.16126651]

>>16126585
This is a question about sagemath syntax, not a science question. Surely there are boards or a discord or similar for that software.

[Anonymous No.16126765]

>>16125091
Now that you pointed that out, I am getting unitless for both b(r) and d. But looking at the paper with the pic in >>16124381, it calls phi the local magnetic field. Is it correct to refer to it as this and d as a unit dipole if they are actually unitless?

[Anonymous No.16127013]

>>16125929
so if i just take n_{k}>max{n1,n2,...n_{k-1}} then it'll work?

[Anonymous No.16127098]

any anons would like to help with this >>16125996

[Bargle. No.16127100]

Wut?

[Anonymous No.16127104]

Is this the right thread for asking AI related questions or is there another board for that?

[Anonymous No.16127106]

I planned to have an AI on my local PC to answer all my questions.
I don't want to use ChatGPT or something like that because, if I understand correctly, all the questions are being saved on their servers to "improve" the AI.
I don't want my questions to leave my local PC, but I would want an option to "update" my AI with new data so it would have fresh data now and then.

Is something like that possible?
Even if you don't have the right answer, maybe you can guide me in the right direction at least.

[Anonymous No.16127126]

>>16127106
try /lmg/ over on /g/

[Anonymous No.16127129]

>>16126206
if you double the voltage across a resistor, you also double the current through it, hence the voltage squared proportionality. basically you get [math]P=\frac{V^2}{R}[/math] by combining [math]P=VI[/math] and [math]V=IR[/math].
however, this naive application of ohm's law doesnt perfectly apply when we're trying to transport power. if we double the voltage, we actually want the current to *halve* (roughly) in order to maintain constant power supplied. we do this using transformers (picking the appropriate transformer ahead of time, knowing what your input voltage will be). obviously if you have two resistors in series then we wont be able to do this, but for a constant load (a neighborhood, eg), transforming the voltage down to 120V will ensure that the load draws the same power no matter what voltage we throw in the transformer.
let [math]V_S[/math] be the voltage the plant is providing, [math]V_L[/math] be the voltage going into the load transformer, [math]P_L[/math] be the power the load is consuming, and [math]R_C[/math] be the resistance of the transmission lines. we know that [math]P_L=V_LI=(V_S-IR_C)I[/math] must remain constant. what happens if we halve the current [math]I[/math]? since [math]V_S[/math] is the only other non-constant in the equation, it will have to change (increase, namely) in order to compensate.
[math]\displaystyle
P_L=(V_S-IR_C)I \\
P_L=V_SI-I^2R_C \\
V_S=\frac{P_L+I^2R_C}{I} = IR_C + \frac{P_L}{I}
[/math]
the left term is the voltage drop across the transmission lines, and the right term is the voltage drop across the load. notice that halving the current will cause the source voltage to increase if the voltage drop across the load is bigger than the transmission lines (it is), but the voltage wont literally double unless [math]R_C[/math] is zero. if we halve the current but *not quite double* the voltage of the source, the plant must now necessarily be outputting less power while still supplying the same power to the load.

[Anonymous No.16127159]

>>16127126
thanks

[Saint. Barkon No.16127168]

>>16127159
There's a few spiritual points on me where you can see what I truly say like ones near my hip, it's my aggression. And there's a joke one.

[Anonymous No.16127385]

/sci/anons have you ever desired the opportunity to beat soientists up?

I stumbled across an old playstation 2 game called whiplash where you play as two escaped lab animals chained together.

You can play it on a pc using a ps2 emulator such pcsx2.

Hearing "Stop in the name of science" as you bludgeon the hundredth clip board and lab coat wielding sience cultist doesn't get tiring in the slightest.

[Anonymous No.16127399]

>>16109209
possibly retarded question:

How much energy is stored in your average cloud over a given surface/volume and over a given length of time say a day, and can we replicated this phenomenon by pumping salt water or other water based solutions on 2 opposite sides of a membrane.

the 2 solutions would similarily to the clouds, be of different pressure, temperatures and of opposite charges with a hopefully high difference between the 2 to achieve enough power to harnes the electricty potential difference as current.

apparently there are salt water batteries attempting this idea, but I was thinking more of a generator.

[Anonymous No.16127457]

Let X be some (finite?) set, let [math]F(X)=\bigsqcup_{1\leq n<\infty} \bigsqcup_{1\leq i\leq n-1} F_i \times F_{n-i}[/math] be the free magma over X, where [math]F_1=X[/math] and [math]F_n= \bigsqcup_{1\leq i\leq n-1} F_i \times F_{n-i},\text{ for }n\geq 2[/math].
I was trying to calculate the cardinality of these [math]F_n[/math] and was given the hint to set up a functional equation for [math]f=\sum_{n\in\mathbb{N} } |F_n| X^n[/math]. I was wondering how I could've seen that myself? Is it common to set up these kind of functional equations to find the cardinality of such recursively defined sets? I probably would've just tried it with induction and failed miserably.

[Saint. Barkon No.16127860]

Is psychological really meant to be psycho creative because I see no logic to the human psyche bar the psyche itself.

[Saint. Barkon No.16127869]

>>16127860
No, sorry. It's a perfect cut. It's psycho logical, the psyche is an expansive topic and the creative logic is included as well as pure creativity.

[Anonymous No.16128066]

Hello fellas.

I'm currently working with timeseries applied to healthcare. I want to do mortality prediction in ICU cares using timeseries data.

After some preprocessing I ended up with a table whose columns are hadmission_id, a timestamp , EHR features with numeric values and if the patient died or not.

My question is, with this data how can I predict if a patient dies or not? How else should I preprocess it? It's confusing me because there can be a lot of the same values for the same feature for the same timestamp, the only thing identifing the patient really is the hadmission_id

[Anonymous No.16128083]

How the hell do multimmetres measure cuurent? What are they actually reacting to?

[Anonymous No.16128095]

Is there anything math-related fun to grind that doesn't need a lot of theory? I'm ADHD retard on Adderall and need something stimulating to do.

[Anonymous No.16128105]

>>16128095
Project Euler? It does require some very basic coding knowledge but even that isn't required for the early questions and almost no theory either. It does (very) slowly get progressively more difficult but that's part of the fun, learning some math to make your programs run faster.

[Anonymous No.16128116]

>>16128095
I suggest you go to the mall and grab a girls asshole and put your finger inside her butt

[Anonymous No.16128119]

>>16128105
noice, thank you
>>16128116
I don't get the euphoria to hit on random women outside anymore

[Anonymous No.16128124]

>>16128119
It's too late for you to do that if you're over 21.

[Anonymous No.16128142]

>>16128105
so for the first,
>Find the sum of all the multiples of 3 or 5 below 1000
thought starting at the highest number, try 3 and 5, if it returns float, keep going, if it doesn't then divide until 1 and keep every remainder except 1 as multiples so I can skip them.
>keep every remainder except 1 as multiples so I can skip them.
I assume this is good to avoid wasting CPU but from memory I can't recall how I would do it in programming, should be easy to quickly figure out though.

Is this how you should do it? I'm a retard so I don't even remember basic stuff like this that I'm sure there are plenty of 'algorithms' to apply

[Anonymous No.16128184]

>>16128142
> Is this how you should do it?
There is rarely a right way or a single way to answer the questions. Once you get the correct answer you will be linked to a discussion board for that question and people will list the code for how they solved it and talk about the various methods. You can learn more from that.

[Anonymous No.16128227]

>>16128142
1. Arithmetic sequences. The multiples of 3 are 3,6,9,12,...; there are 333 of them below 1000. The sum of an arithmetic sequence is the mean of the first and last values multiplied by the number of entries. So 333×(3+999)/2=166833. The same approach can be used to calculate that the sum of the multiples of 5 is 99500. And that the sum of the multiples of 15 is 33165.
2. Inclusion-exclusion principle: the size of the union of two sets is the sum of the sizes of the individual sets minus the size of their intersection (because if you just add the sizes of the two sets, those in the intersection get counted twice). So you need to subtract the sum of the multiples of 15 from the other two sums to get 166833+99500-33165=233168.

Note that >>16128105 is talking out of his ass when he says that you don't need theory. PE is almost entirely mathematical theory. The first few problems can be brute forced: for the first one, you could just write a program which loops over the numbers 1...1000, adding it to the total if the number is a multiple of 3 or 5 or both. But later problems are designed so that a brute-force approach won't finish before the sun goes supernova, so you have to use mathematical theory to replace long loops with closed-form expressions. Combinatorics and modular arithmetic both feature heavily. I did the the first 300 or so problems, but the later ones often boil down to recognising a specific mathematical theorem which can be applied to the problem; if you don't know of the theorem or don't make the connection, there's no way you'll solve it.

[Anonymous No.16128231]

>>16125996
have u tried plugging in random numbers and check yourself?

[Anonymous No.16128237]

This is more of a biology question but is it normal for me to be capable of inducing syncope? All I have to do is just inhaling lots of air and I start losing my senses and control. Next thing I know is I'm collapsed on my bed (or ground), not knowing where am I, what time is it and how I ended up there.
I looked it up but couldn't find something on it. My best guess is lungs expanding to the point of pressuring and reducing blood flow of heart enough to cause fainting

[Anonymous No.16128309]

>>16128227
I disagree. Most of those early questions can be answered with brute force calculation alone (anything with a difficulty of 5%). Sure it make take minutes or hours instead of a few seconds if you know the relevant math theory, but my point stands.

[Anonymous No.16128527]

>>16128231
yeah it doesn't work, but I also can't figure the mstake I'd made. Trying the derivazion again, I got:

[math]\frac{\sin \frac{(n+1)\beta }{2}}{\cos \frac{\beta }{2}}\times \cos \left( \alpha +\left( n\right)\frac{\beta }{2} \right)[/math]
which also seems to not work for the series of angles, pi/4, pi/2,3pi/4

[Anonymous No.16128549]

>>99979513
I'm close to having a panic attack because I didn't study for exams. With one day left, what do I do?

We had an assignment due a day before the exam, and it took way too long for me to complete it, so I couldn't study.
We have three exams, one each day for the next three days, starting tomorrow. Each accounts for 35% of the grade of the module and covers four lectures. What do I do, anons? I just finished the assignment, and now I haven't studied at all for the exams. I'm freaking out. I was a lazy bum who didn't study early, and now I'm panicking. Please help; I need advice.

[Anonymous No.16128562]

>>16128549
If you've left it to this late then there's fuck all you can do. So you calm down. Accept you're going to fail. Plan for your resits. And next time don't be such a lazy fucking idiot.

[Anonymous No.16128777]

I'm trying to find a plot of color temperature at dawn. I know over the course of a day it's a curve from warm at low inclination to bright at zenith but there's a cold blue period before the sun clears the horizon and I want details.

[Anonymous No.16129127]

I'm in space smacking identical, inelastic rods with my hammer. I line up perpendicular with some varying point on the rods and hammer them in a uniform way.

It's my understanding that the center of the rods will travel away from me at the same rate no matter where I hit them with my hammer. However, the rods will rotate more or less depending on where I hit the rod. It's my understanding that rods traveling linearly at the same rate, but rotating at different rates, have different kinetic energy.

How is it consistent with conservation of energy that I can create rods with different amounts of kinetic energy by hitting them in a uniform way?

[Anonymous No.16129165]

>>16129127
For conservation of energy, the hammer is part of the system. Your attack may be uniform but the motion of the hammer after impact is not.

[Anonymous No.16129176]

>>16129165
I'm hitting the bar as quickly as I can then withdrawing the hammer. Since I'm always hitting the bar perpendicularly and over a short distance, the impact should be very similar.

I get that it's not literally uniform because I'm pushing over some tiny distance while the bar spins, but does that tiny difference really account for the entire energy of the spin?

[Anonymous No.16129597]

Can an anisotropic speed of light explain the EPR paradox?
>suppose all light moving straight away from (you) moves infinitely fast
>suppose all light moving straight toward (you) moves at 1/2 c
>implying, quantum collapse is both instantaneous and non-superluminal

[Anonymous No.16129612]

>>16109209
Is it possible to microdose a nerve agent? Strictly on a theoretical level.
I was watching a youtube video a while ago about nerve agents, and the guy said that there is a certain nerve agent which crosses the blood brain barrier, thus directly firing the nerves in your brain. If there was a way to measure out a non lethal amount of a nerve agent and directly inject it into your brain, what would it feel like? Would it get you high? What if you put it on your dick, would you get a boner?

[Anonymous No.16129698]

is gaining intutions about your field just a matter of experience or is there an insurmountable gap in intelligence between those who can intuit shit at a glance and those who can't?

I'm two years into a PhD in genetics and recently presented some very confusing results that I've been struggling with for months at a seminar, and the people there just correctly figured out what was going on with it on the spot

I was fine when my advisor did it because he's an experienced professor but the guy who figured everything out is a postdoc my age. I didn't even understand what he figured out during the seminar, I had to go over what he explained over the next two weeks to get it. it really was a blow to my self confidence.

[Anonymous No.16129701]

>>16129597
Lol what are you writing you crumb. These niggerkikes writing the good books always put 666 in the barcode number.

[Anonymous No.16129707]

>>16129698
> is gaining intutions about your field just a matter of experience
Yes. Sure there are rare, special individuals but 99 times out of 100 it is simply experience. I remember going over some of my old school and undergrad mock-exams. Stuff I struggled for weeks, even months, to understand, sometimes failing. Now I could do them all in minutes.

[Anonymous No.16129867]

[eqn]\int_0^\infty dx\, \frac{x^3}{e^x-1}[/eqn]Can you evaluate this integral using the residue theorem?

[Anonymous No.16129870]

>>16129698
There are legitimate geniuses, but most of the time it's people having seen a very similar problem before and then simply using that experience to solve the one at hand. Don't think too much of it.

[Anonymous No.16129966]

>>16129707
>>16129870
thanks guys

I'll keep going and hope the intuition comes

[Anonymous No.16130074]

I was curious but couldn't find much info on Tesla's "longitudinal" waves aka non-Hertzian waves and some kind of schizo theories about longitudinal magnetic dielectric transmission that PI/2 times faster than the speed of light.
Did Tesla dabble as a schizo or that's some modern interpretation of his experiments?
Also https://en.wikipedia.org/wiki/Charles_Wheatstone is often mentioned as a legit inventor and a scientist who also supposedly measured this PI/2 * c nonsense.

[Anonymous No.16130086]

Don't know if this is the right place for this but I can't for the life of me understand why my plot output isn't linear. The freq values are supposedly on a log10 scale but I'm too retarded to know if I should use that in any way besides my plot.

clear
close all
clc
freq = [1000;3000;9000;50000;93000;223000;510000];
amp = [79;71;59;49;39;33;24];

Sxy = sum(freq .* amp);
Sx = sum(freq);
Sy = sum(amp);

SSxy = Sxy - (Sx*Sy) / length(freq);

Sx2 = sum(freq .^ 2);
SSxx = Sx2 - ((Sx^2) / length(freq));

a = SSxy / SSxx;
b = mean(amp) - a * mean(freq);


y_pred = a * freq + b;

mare = (sum( abs(amp - y_pred) ./ amp) / length(freq)) * 100;

SSE = sum((amp - y_pred) .^ 2);
SST = sum((amp - mean(amp)) .^ 2);

r_sqr = 1 - (SSE/SST);


semilogx(freq,amp,'-r')
hold on
semilogx(freq,y_pred,"b-")
legend('Given Data','Optimal Line')
title('Given vs Optimal Amp-Freq Plot');
xlabel('Frequency,Hz');
ylabel('Gain, dB');
hold off

[Anonymous No.16130107]

>>16129867
All you need is the geometric series formula.

[eqn]\int_0^\infty \frac{x^3}{e^x - 1} dx \\
= \sum_{n=1}^\infty \int_0^\infty x^3 e^{-n x} dx \\
= \sum_{n=1}^\infty \frac{1}{n^4} \int_0^\infty u^3 e^{-u} du \\
= \zeta(4) \Gamma(4) \\
= \frac{\pi^4}{15}[/eqn]

[Anonymous No.16130127]

>>16128527
>>16125996
any brocels who would like to help me out

[Anonymous No.16130146]

>>16130086
I just had to add freq = log10(freq) after initializing freq.
Fuck I'm retarded.

[Anonymous No.16130202]

Can anyone prove proposition A1.6? (D is the set of finite decimals).

[Anonymous No.16130245]

>>16129698
>a postdoc my age
>two years into a PhD
These are very different levels of experience, at least in my field. A postdoc is closer to the experienced professor than a baby grad student. Literal age doesn't matter.

[Anonymous No.16130413]

are there any mathematical models to properly describe the mechanism and how to build a trompe pump?
an example of the technology
https://www.youtube.com/watch?v=uvf0lD5xzH0

[Anonymous No.16130414]

>>16130413
>pump
well it's not really a pump it's more of a passive air compressor

[Anonymous No.16130805]

https://i.4cdn.org/wsg/1712921488692430.webm

[Anonymous No.16131048]

What topics do I need to learn before I can work in a.i field?

Im an EE major but I was thinking of shifting to comp sci and take some classes for data science

[Anonymous No.16131079]

Is there any merit to the idea that all matter is just very tiny particles moving really fast in spinning motion and this scales up all the way to macro level?

[Anonymous No.16131251]

>>16131079
Particles don't spin so your premise would appear to be fundamentally flawed.