/sci/ - Science & Math

Why am I so shit at life?

how. I assume I have to use expectation maximisation but how

>>9442815
You don't meditate.

>>9442955
>how. I assume I have to use expectation maximisation but how
What have you tried?

>>9442967
well for now I'm rereading the notes of expectation maximization, the part I don't understand is where the additional L2 norm would fit in in all this

Should I ask about neural networks and back propagation here?

>>9442996
>neural networks and back propagation
not science or math

recommend a brainlet (me) a book on theoretical physics. not for a specific subject, a text that gives me an idea of how theoretical works. something that explains why we integrate here or use a fourier transform there. that kind of stuff

>>9443012
But /g/ is a shit board. Where should I look instead?

>>9442975
nevermind I'm dumb, all I have to do for this exercise is derivate the given equation w.r.t u_k, it's actually easy as fuck

is STEM even worth anything anymore? I'm in EE and I'm probably gonna finish my program, but I'm so fucking cynical when it comes to employment prospects after graduation.

>>9443012
>he doesn't understand neural networks
Yes they most certainly are both science and math, so fuck off

>>9443021
What is your question anon this is the correct board, /g/ is for technology and there are some programming kiddos but here is where the Computer Scientists lurk.

Even if butthurt engineers like
>>9443012

Say different

>>9443060
>>he doesn't understand neural networks
I'm not a "he".

>>9443075
fuck off faggot

>>9443079
>fuck off faggot
Why the homophobia?

>>9443060
>>he doesn't understand neural networks
I'm not a "neural networks".

>>9443075
>>9443084
>i'm not a "he"

>>9443084
honestly it was interesting the first 10 times, by now you're just a tiresome fucking faggot.

>>9443105
>honestly it was interesting the first 10 times, by now you're just a tiresome fucking faggot.
Your homophobia was never interesting.

>>9443109
>>9443084
okay buddy I'll still play with you
Why the faggotry?

>physics 1
>find the time of a ball thrown in the air that reaches a max height of 5000feet.
>spend 15minutes thinking about it
>cant figure it out
>look up answer
>set vf to 0 at its peak

if i didnt realize that, am i fucked the rest of the semester?

>>9443113
>okay buddy I'll still play with you
>Why the faggotry?
Are you okay?

>Integer linear programming

can anyone do this?

>>9443129
>can anyone do this?
What have you tried?

Where do you guys get your textbook torrents? Are there any sites other than libgen?
I'm looking for Information Systems Today: Managing the Digital World 7th edition. Can only find 5th and 8th.

>>9443126
I'm not the one yelling for attention in every thread you can. Every regular poster is annoyed at your shit at this point. Here's your (you)

>>9443133
not much, this was an exam question and its pretty hard

>>9443144
>Every regular poster is annoyed at your shit at this point.
I don't mind annoying someone who unironically considers themself a "regular poster".

>>9443136
Usually libgen and bibliotik
your book is not o bib tho

>>9443119
That's why I struggle so hard with physics too.
I can't solve a single damn "hard" problem from those undergrad textbooks out there because I couldn't find the "trick"

What do you guys think about theorems that are almost always true?

For example, I see that Goldbach's "other" conjecture:

https://projecteuler.net/problem=46

It seems to only have two exceptions (5777 and 5993). Some guy on the problem's forums claims to have checked up to 2*10^13, but I have not seem his work.

It seems interesting that some statements are almost always true, but there are weird exceptions to those rules.

>>9443119

Most physics problems are variations on a familiar theme. I think if you do enough of them (and pay attention to exactly what was done, and find patterns in the solutions that extend beyond any single problem) you'll do fine.

>>9443169
by regular poster I mean anyone who regularly reads, maybe not even posts in, threads. anyone who browses /sci/ regularly finds you a tremendously annoying faggot who just has to yell hit catchphrase in every thread you can

We have a joint PMF:
[math]P(X=m, Y=n)=\frac{e^{-7}4^m5^{n-m}}{m!(n-m)!}[/math] for m = 0,1,2,...n and n=0,1,2,3,...
I want to find the marginal PMF for x,y so I do:
[math]P_x(m)=\sum_{n=0}^{\infty}\frac{e^{-7}4^m5^{n-m}}{m!(n-m)!}[/math]
[math]P_y(n)=\sum_{m=0}^{n}\frac{e^{-7}4^m5^{n-m}}{m!(n-m)!}[/math]
I can't see any way to reduce these further, but it just feels like there should be more to this problem. It also asks if X and Y are independent; it doesn't appear to me that these marginal PMFs would become the joint PMF when multiplied. I just feel really weird about this whole problem

>>9443197
>anyone who browses /sci/ regularly finds you a tremendously annoying faggot who just has to yell hit catchphrase in every thread you can
Speak for yourself.

>>9443201
>>9443197
>>9443169
>>9443144
>3
>>9443126
>>9443113
>>9443109
>>9443105

Please shut the fuck up you flaming faggots

>>9443197

I'm not a "regular poster", so maybe I don't have the authority to say this, but I think you should take a deep breath.

You are triggered as fuck, bro

>>9443176
Damn, how can the 8th edition be up but no sign of the 7th? shieeeeeeeeeeeeee I'm fugged

>>9443210
>>9443209

>>9443136
i checked b-ok.org and unfortunately they only have 3rd edition.

id try torrenting if youre desperate enough (not on uni property tho)

>>9442996
>>>/sci/thread/9441598

>>9443221
What do you mean try torrenting? Don't these use torrents? Is there a torrent aggregator for textbooks? I just need to know if the book is out there before I call it quits.

I have no question I just want to point out that my physics professor is a huge bitch who wouldnt accept my project last semester because he figured out I downloaded an article through sci-hub (sci hub lets you get paywall articles for free). Apparently that ruins the integrity of it. Fuck this guy, Im not paying $35 for an article.

Before you say anything, our uni only has subscriptions to certain journals, not the one I needed

>>9443241
>my physics professor is a huge bitch who wouldnt accept my project last semester because he figured out I downloaded an article through sci-hub
How did he find out?

>>9443238
Hi I found the 7th edition

https://avxhm.se/ebooks/12920980661292098066.html

Not I have NOT tested the downloads

>>9442805
Barry is a qt but god his handwriting is fucking terrible

If I already have AIDS is there way I can get a "worse" strain AIDS from further use of unprotected sex/dirty needles?

>>9443258
>https://avxhm.se/ebooks/12920980661292098066.html
Trying it out, you're a gentleman and a scholar.

>>9443254
He repeatedly asked me where I got the article. I was able to kind of bullshit an answer at first but he took me into his office and asked me seriously so I didnt have the balls to lie at that point

>>9443262
Requires payment to download

>>9443271
Nope, downloading atm, just super slow. Unless you mean the pdf file is just an ad with a link. Pls say it ain't so~~

>>9442805
How to [math]x^{x}[/math]
How to solve equation with that term? How to integrate, differentiate it? Just let me know the topics I should study to be able to do it

question for those in physics

when youre reading a text and the author is laying out theory, they might go from an integral to a result or another equation without explaining how. how often do you work out that integral on your own?

>>9443258
>>9443271
>>9443277
Just finished downloading it, THAT'S THE ONE MOTHERFUCKER THANK YOU SO MUCH! How did you find it?

>>9443341
I searched it on that site. Glad I could help

>>9443291

Consider z = x^y. Use elementary calculus. Find the directional derivative along the line x = y. That's for the derivative.

Still thinking about the integral.

>>9443199

I havent done any work on it, but could you consider the random variable x = n-m? Then it looks like the probability density for two indep. Poisson variables. The sum of two Poisson random variables is Poisson, you can do some trick like that.

>>9443363
??? the derivative is super simple, use the exponential

>>9443367

lol, I'm not sure what you mean. Is there something obvious I'm missing?

The derivative is x^x + ln(x) x^x. One part comes from d/dx (a^x) term, and the other part comes from the d/dx (x^a) term. Set a = x.

Can you somehow do this more easily?

>>9443367
Maybe you mean look at the logarithm of both sides, implicit differentiate, etc?

If so, I like this other method. It shows you how it really just reduces to simple rules you already knew.

Let A_1, ..., A_m be subsets of {1, ..., n} such that for all i, j, A_i is not a subset of A_j.

Show that
[eqn]\sum_{i=1}^m \frac{1}{\binom{n}{|A_i|}} \leq 1[/eqn]

Any idea ?
I think I could prove it combinatorially when the sets all have the same size, but that would be ugly and incomplete. There should be a clever solution.

>>9443375
>>9443378
x^x = e^(x ln(x))

>>9443396
jesus im a moron

>>9443404
nah mate it's dumb trivia that one has to see sometime

>>9442805
How do I prove the law of total probability when the universe is partitioned into more than two events? Is it an induction?

>>9443414
it follows from the definition of a probability space, I'm not sure how you would prove it

>>9443382

I'm looking at this one. I hope my progress isn't too trivial so far, but I can prove the case when m < n.

Since 0 < |A_{i}| < n (strict inequality), (n choose |A_{i}|) > n, so that 1/(n choose |A_{i}|) < 1/ n, so since m<n, that sum is also less than one.

If m > n, that'll put some kind of bound on the size of the set. You need the size of the sets to be near n/2, or else there is no way to satisfy the condition. The solution feels close!

>>9443291
x^x is by definition exp(x*log(x))

>>9443382

Sorry bro, I'm not really getting anywhere. The case where all sets have the same size is pretty trivial, since there are at most N choose S of them, where S is the size of the sets.

I have an ugly proof if there are two sizes of sets, S_1 and S_2.

My advice would be to think about conditions on the sets if m > n. You should find that they are forced to crowd around n/2, which will force those denominators to get rather large rather quickly.

How bad would it be if some sort of natural disaster prevented people for turning of and completely disassembling one or several nuclear reactors. It takes a while for all fuel to be removed, capsulized and finally buried in an extremely secure and stable underground storage sites where they won't be disturbed for thousands of years. The only reason fukushima and chyrnobyl didn't saturate large amounts of earth with radioactive materials is because people were able to attend to them. How bad would it be if they were left completely unattended and let burn for several weeks, or perhaps even a month? How bad would the fallout be?

>>9443052
That's not exactly the problem. Employers definitely "value" your degree; finding a job in the field without one would be very much harder.
But they also value the degree of the other 150 people that applied for the entry-level position you want.
The fact that people can say with a straight face that 50 job applications is "not trying hard enough" is absolutely absurd but they're not wrong.
No matter how great you did in uni the job market is 100% a lottery without connections anymore and the only way to win is to spam everywhere until they pick you out of the pile for no good reason.

>>9443264
>My friend how majors at a different university downloaded it for me
How difficult is that?
Also, I don't think there is a single professor at my university who will give a fuck where you got the article from.

>>9443708
He wouldnt have bought it. This guy is hardcore, he doesnt take bullshit. Hes some big theory guy, authored multiple textbooks. Plus hes in charge of the graduates so Im not about to risk my future lying. Id rather have to retake a class than get kicked out

>>9442805
Guys, Barry Simon Is A Real Person.

Go ask HIM PERSONALLY, if you actually have 'stupid question' that are on HIS level.

>>9443382
Idk if this helps, but if you take a random permutation of {1,...,n}, the expected number of A_i it preserves is given by the left hand side. This is just linearity of expectation, since, e.g., the probability that a random permutation fixes A_1 is 1/(number of subsets of size |A_1|).

I have no idea why a random permutation should only be expected to fix at most one A_i, but this really feels like a linearity of expectations problem, and that's the easiest way to use it.

>>9443510
Anon, there are n choose 2 (way more than n) subsets of size 2, and none contains another.

Lads, i want to find all journals about africa ranked by impact factor (or something else relevant). I am clearly not a uni student/professor and don't know how to go about this. google isn't helping much. How do I do it lads?

So is everyone here just a mediocre student social loser? Who would use this site except outcasts?

>>9443763
I Can Verify That Stephen William Hawking Has Been Visiting 4chan.org/sci/ For A Lot Longer Than Simon Troy Cosgrove Has.

... oooh.

>>9443751

That's true, but "way more than n" is relative. N choose N/2 is much larger than N choose 2. If m is on the order of N choose N/2, this suggests you have to use sets of size N/2, which rules out many sets of size 2.

For very large m, the sets must be near N/2.

Or am I not seeing your point?

pretty bad with physics so stuck on this problem which i guess is pretty 101. if you were to close the switch in this circuit, why does it increase current and voltage? i thought it would decrease the voltage since it offers a shorter path to return to the battery. also why does figure 2 in the circuit turn off/become more dim?

>>9443169
>>9443126
>>9443109
>>9443084

Kys FAG

>>9443851
Now THAT, my fellow anons, is 1 True 4channer post here, my kinda pal.

>Underestimated the time I would spend studying
>Now I'm way behind schedule and feel like I'm going to fail all my classes
I study too slow and I'm a brainlet. Please tell me to kill myself.

>>9443090
Tits or GTFO.

>>9443060
My question is where to start, what to read. I know some programming languages, but am new to neural networks so I don't really know what to do.

If you have a 3x3 matrix with 3 independent column vectors and the determinant is nonzero, does that mean the matrix has no solutions?

Hey /sci/, how likely is it for me to learn math up to a calculus level in say 6 months from a geometry level. I need all the help I can get to pull this off. Any good reasorces or videos to watch?

>>9444305
Also I haven't taken a math class in 5 years, is there hope bros? I don't care how hard I have to work, I just want to finish school

>>9444305
>>9444307
Was in the same situation anon, a year ago I hadn't been to school (thus taken a math class) in 6 years. Got to Algebra II back then but forgot most of it.

Use Khan Academy to take tests and Google/Youtube to find good tutorials (KA has some good ones but I doubt you'll want to watch 50 3 minute videos a day as opposed to one hour long lecture.)

I'm up to Calc now (though struggling a bit) and its only been a few months. You'll make it anon.

>>9443808
what do you mean by decreased and increased voltage, are you talking about across R1 and R3?

current will increase because R2 is shorted out of the circuit, thus decreasing the total resistance of the circuit. Since the voltage on either side of R2 is the same, there is no voltage drop across R2. If you want you can also remember that the equivalent resistance of resistors in parallel is smaller than the smallest resistor, since the smallest resistance of the switch and R2 is a short, the equivalent resistance is 0.

using KVL or Faraday's law we can see that the voltage across R1 and R3 must increase since the voltage across R2 will decrease. The voltage supplied by the source will also decrease unless we consider it to be ideal, but we probably can just consider it ideal and not worry about it.

Since the voltage across R2 has decreased, the current through R2 must also decrease meaning that it gets dimmer or turns off since there is no current through it.

>>9444272
A matrix doesn't have solutions. What are you talking about?

>>9444272
>does that mean the matrix has no solutions?
This is a meaningless notion.

>>9444049
Adderall, friend.

>>9444272
These
>3 independent column vectors
>determinant is nonzero
>the kernel of the matrix is {0}
>the image of the matrix is the whole space
>3 independent row vectors
>0 is not an eigenvalue of the matrix
as well as other stuff, are equivalent
so, yes

I have a function that's in the form of v^2*(abc) and I need to figure out the maximum error as I know the tolerances of a, b and c, I did the partial differentials but the error is still dependent on the variable v which represents velocity, how would I go on to have the maximum error? Discard the variable by setting it as 1? Displaying the error as a function of velocity?

>>9443199
They are clearly dependent since X can only be as large as Y, and therefore X depends quite literally on Y. Otherwise, you can draw the support of a joint distribution, and if it's not rectangular, you can rightly conclude they aren't independent, as in this case, but we can find a marginals regardless.

[math] P_{X}(x)= e^{-7} 5^y\sum_{x=0}^{y}\frac{(4/5)^x}{x!(y-x)!} [/math]
[math] e^{-7}5^y(\frac{1}{0!y!}+\frac{(4/5)}{1!(y-1)!}+\frac{(4/5)^2}{2!(y-2)!}+...+\frac{(4/5)^{y-1}}{(y-1)!1!}+\frac{(4/5)^y}{y!0!}) [/math]
[math] \frac{e^{-7}5^y}{y!}(\frac{y!}{0!y!}+\frac{y!(4/5)}{1!(y-1)!}+\frac{y!(4/5)^2}{2!(y-2)!}+...+\frac{y!(4/5)^{y-1}}{(y-1)!1!}+\frac{y!(4/5)^y}{y!0!}) [/math]

So remember [math] {y\choose r} = \frac{y!}{r!(y-r)!} [/math] and that [math]
(a+b)^n=\sum_{k=0}^{n}{{n}\choose{k}}a^kb^{n-k} [/math] and go from there.

>>9443129
can someone answer this? im curious as to how you would actually write it out. i have an algorithm in mind

which one?

>>9444751
3rd from the bottom, brainlet

can someone explain the process at solving this?

>>9443012
how fucking dumb are you

>>9444948
>how fucking dumb are you
What do you mean?

>>9443136
I find most shit I need on soulseek, it's a complete lottery though

>>9443757
look up the Mpemba effect, it's Africa's main contribution to modern science

>>9444966
read a book

Total brainlet here, i must send a paper to a teacher, we are working in groups but my classmate did not work at all so i'm fucking late.
Problem:
find the maximum volume of a cuboid with theses constraints :
no edge should be greater than 1 meter.
the sum of the different edges L + l + H should not be greater than 1.5 meter.
I think i should use a multivariate function but i never did that in my life.
I think the volume is [math] f(x,y) = x \times y \times (1.5-x-y) [/math] but this function is not defined for every x and y and i have no idea how to derive this and it may be totally wrong here.

Wolfram tells me that lim (x,y)->(0,0) ((x^3)(y))/(x^6+y^2) doesn't exist, but it times out so it isn't reliable. When swapped with polar coordinates (pic related), however, it says it tends towards 0, but somehow I'm not getting that result through my calculations. Any help?

>>9442805
LIGO has detected gravity waves. Awesome! Most if not all of our astronomical observations have been EM (radio through gamma+) photons.
LIGO detected the gravity waves with "L" shaped laser configurations bouncing off mirrors.
Gravity waves are a ripple in spacetime. A distortion that warps the space between LIGO laser source and detector.

Q: How did LIGO detect that warping ripple of space with a laser beam? Did the beam follow the curve of the ripple as it passed and therefore take longer to travel the distance between laser source and detector in that moment?

>>9445052
Just plot it to see that [math]y=\pm x^3[/math] are interesting curves and give limits [math]\pm 1/2[/math]. You get a third limit along x=0 or y=0, too.

If the Universe is accelerating, how is Hubble's law true?

>>9445099
They didnt detect gravitational waves hahaha that experiment was a sham

>>9445099
Gravitational waves passing by an object cause spacetime to contract and expand, perpendicular to the direction of the wave. The GWs passing by cause stretch one arm, while compressing the other. Light is affected slightly differently so LIGO can measure this.

Gravity waves are something different.

>>9445284
And I suppose it was just coincidence that the detection was used to find the first nearby kilonova, just at the right distance and in the right place? Moron.

>>>/x/

Just because you don't understand doesn't make it wrong.

>>9445300
>believes in space-time
>calls someone else moron

>>9445301
You didn't answer my question.
>And I suppose it was just coincidence that the detection was used to find the first nearby kilonova, just at the right distance and in the right place?

>>9445361
Okay. A quick debunking of the LIGO thing.

It is claimed that the g waves shoot out of the ends of the spinning neutron star. And then it is claimed that there is a g wave every 360 degrees of rotation. This is contradictory. If g waves are shooting out of the ends of the star, thats 2 waves per 360 degrees. So already they dont know what theyre doing.

The next issue is what is creating the wave? waves have a frequency. What is creating the frequency? They claim its that one star blocks the other (like an eclipse). This is impossible because gravity doesnt get blocked. An object cant block gravity like it can light.

And they didnt use g waves to locate the knova, they used gamma radiation

>>9445370
>It is claimed that the g waves shoot out of the ends of the spinning neutron star.

These are two merging neutron stars.

> And then it is claimed that there is a g wave every 360 degrees of rotation.

No it's not. Gravitational waves are a continuous, classical wave. The waves are emitted the whole orbit.

>The next issue is what is creating the wave?

The mass accelerating, specifically a changing quadrupole moment. In the case of merging neutron stars it's the stars orbiting each other.

>What is creating the frequency?

The major frequency is the frequency of the orbit.

>They claim its that one star blocks the other (like an eclipse).

No they don't.

>And they didnt use g waves to locate the knova, they used gamma radiation

Wrong. The gamma rays gave a far worse constraint on the sky than the LIGO detection and they didn't give a distance.

Literally every argument you have is based on a misconception. You have clearly done no research on the subject whatsoever, but feel qualified to "debunk" it.

>>9445383
>>9445370

Here is the sky localisation, showing how much better LIGO was than the gamma rays. Note the Swope survey got to the kilonova first by selecting galaxies at the distance given by the LIGO alert.

>>9445383
>being this wrong

I mean all you did was deny everything.

If you just go to the "neutron star merger" wiki youll see how wrong you are. Just a surface level wiki article contradicts what you just said.

Note from the wiki
"pulse of gravitational waves"
Thats because the 2 stars circle around each other. So you, the observer, see an eclipse. There is a point where one star blocks the other.
This is where the "pulse" comes from, the claim is that gravity gets blocked in that eclipse. This is wrong. LIGO did not find g waves if they measured something pulsing

>>9445399
>I mean all you did was deny everything.
No. I also answered your questions. I even provided evidence for the gamma ray localisation bit. When you say "they say this", I can only tell you that you are wrong.

If you really believe any of those claims I disputed then find an exact citation.

>"pulse of gravitational waves"

Lol. Nice of you to crop the quote in order to hide the meaning of the sentence.

>On 17 August 2017, LIGO/Virgo collaboration detected a pulse of gravitational waves

"a pulse", singular. The pulse is the whole event, the in-spiral and the merger. Nowhere is "pulsing" or "eclipsing" mentioned.

>>9445416
Thats just semantics.
"Pulse of gravitational waves" describes the frequency of the waves. The waves are being shot out at some frequency. That is the pulse. Just like how your blood pulse isnt characterized by each individual pump, its the collection of pumps. This pulse was the collection of pumps of g waves.

You can deny that if you want but youre still wrong.

Its the true believers who refuse to question obvious contradictions who hold back science

>>9445425
>"Pulse of gravitational waves" describes the frequency of the waves.
Gravitational waves do have a frequency, that is not controversial. But that is not what the article is saying.

https://en.oxforddictionaries.com/definition/pulse

A pulse also means "A single vibration or short burst of sound, electric current, light, or other wave."

In any case, this is a wikipedia article written by a random person. You don't do science by reading between the lines of secondary sources.

If you want to discuss this further then find a real source for these claims about eclipses and whatever else.

>>9445446
Okay just run away I guess bc of the wiki article which directly cites where that info came from. Youre not really running away from the wiki, youre running away from its credible sources

So heres the situation. You have 2 neutron stars circling each other. They are spinning as they circle each other. They are so dense that the spinning causes them to shoot out g waves. These g waves ARE continuous. But the observer (ligo) detects a frequency of them NOT the continuous wave (bc the observer does not match the stars spin, observer is stationary). When the two stars are eclipsed according to observer, the g force is weakened because the front star blocks the gravity from the back star.

This is the description of the situation. Get it from whatever source you want. But thats it.

My claim is that that situation is nonsensical because they measured an incorrect gwave frequency and bc gravity cant get blocked. My claim is that the idea of gravity being a wave at all is nonsense because gravity cant have a frequency because theres no mechanism to create frequency given what we know about gravity (instantaneous, cant be blocked, and so on)

I'm doing a for funsies debate with some doctorate students from my health research centre tomorrow regarding conducting a systematic review and I just wondered
Why is it that we don't really see systematic reviews for biological sciences?

>>9445460
>Okay just run away I guess bc of the wiki article which directly cites where that info came from.
Neither source uses the word "pulse". That's because it's not a quote, or it would be in quotation marks. Maybe read what you cite.
I'm not running from anything, it's a single word on Wikipedia with multiple common defintions. It's not evidence of anything.

>Get it from whatever source you want.
Your entire argument is based on "they say this" but when asked to cite it you just "run away". You're not debunking anything if your entire argument rests on a source you won't provide.

>>9442805
To any chemists out there. Lets say I take an H NMR of BH3. Would the hydrogens couple to the Boron resulting in two peaks or just one ? I'm confusedmas my texbook vaguely mentions that B-11 is NMR active but results in "broad peaks".

>>9444312
Thanks anon! That definitely makes sense. I think I was going wrong assuming that shorting the circuit by closing the switch would decrease voltage, thus decreasing current. I forgot to pay attention to the obvious that resistance decreases which therefore makes current increase

>>9443851
https://www.youtube.com/watch?v=NcZcTnykYbw

Trying to understand Euclid's Lemma.

If [math]gcd{a,b} = 1[/math], Bézout's Lemma can be used to conclude that [math]ax + by = 1[/math], where [math]x,y \in \mathbb{Z}[/math]. Multiplication with [math]c[/math] gives that [math]c = c(ax + by) = cax + cby[/math].
The proof I'm reading then states that it should be noted that [math]cax + cby[/math] is a linear combination of [math]ac[/math] and [math]bc[/math], and it that it thus follows that [math]a|ac[/math] and [math]a|bc[/math]. I don't understand how the proof shows that [math]a|bc[/math], halp plx

>>9446335
[math]gcda,b = 1[/math] should be [math]gcd\(a,b\) = 1[/math]

>>9446335
[math]gcda,b = 1[/math] should be [math]gcd(a,b) = 1[/math]

>>9443015
Any freshman physics book or
https://www.amazon.com/Theoretical-Physics-Dover-Books/dp/0486652270/

>>9443119
Calculus 1: Max at derivative 0

>>9445825
afaik protons only couple with themselves so if you're taking an H NMR of it you'd only see a single peak representing the 3 equivalent protons

>>9446338
>>9446335

What are a, b, and c?

>>9446368
The set of all integer multiples of the [math]gcd[/math] of [math]a[/math] and [math]b[/math].

>>9446368
[math]a, b \in \mathbb{Z}[/math], and [math]a[/math] and [math]b[/math] are relatively prime (i.e., [math]a \perp b[/math]).

Hello. I have only basic knowledge of physics and astronomy, and looking through this thread for "stupid questions" I already feel out of my league. I ask this question out of curiosity. I've googled the question, but every result I've found brings up results for the exact opposite of what I'm looking for.

Are there/is it possible for a small planet (let's say the size of Earth) to orbit a very large star (such as one of the bigger ones in pic related)? Would the gravitational pull of the star destroy the planet in a cosmically short time frame?

All google wants to tell me about is a large planet orbiting a relatively small star.

If two coils are set up as a helmholtz pair and are creating a magnetic field, the magnetic field in the middle is the strongest, however if you are closer to one coil than to the other, why is the magnetic field stronger nearer the edges?

Excuse the bad English.

>>9445156
I've already calculated it that way, and that would mean that the limit doesn't exist, right? So why is it that it does exist when calculated in polar coords?

How do I express [math]\mathbf{r}(t) = \left<\frac{1}{2\pi} , \cos(t), 4\sin(t) \right>[/math] in a Cartesian equation, [math]f(x,z,y)=c[/math]? My attempt gets me [math]y^{2}+\frac{z^{2}}{16} = 1[/math]

>>9446459
[math]f(x,y,z)=c[/math]*

>>9446397
Depends how far away it is.

>>9446397
well, that depends on just how much bigger the mass of the star is
if we're talking about earth and any planet from the 6th pic then any attempt at explaining it in classical manner will probably be wrong since relativistic effects play a major role
it's pretty hard to answer this question precisely

>>9446481
change planet to star, i spaced out

If [math]\sum a_{n}[/math] converges and [math]\sum_{n=1}^{\infty}a_{n} = S[/math], how do I find [math]\sum_{n=1}^{\infty}b_{n}[/math], given that for some [math]N\in\mathbb{N}[/math], [math]a_{n}=b_{n}[/math] for all [math]n>N[/math]. This isn't supposed to be hard, and I know I have all the pieces to the puzzle here. You have to fuck with the partial sums and the indexes don't you? Unfortunately I can't put the pieces together right, can someone help.

Does potential energy actually exist?

>>9446505
Wouldn't it just be
[math]S - \sum\limits_{n=1}^{N} a_n + \sum\limits_{n=1}^{N} b_n[/math]

>>9446377
>a and b are relatively prime (i.e., a⊥b)
Does anyone unironically use this notation?

>>9446526

Yes, potential energy has mass

>>9442805
Would there ever be a way for nanobots to convert living flesh into a synthetic material?

This question is about the group [math]GL_3(\mathbb{R})[/math] comprising the set of [math]3 \times 3[/math] matrices with real entries having non-zero determinant. The operation of the group is matrix multiplication.

Show that the set [math]M_3[/math] of [math]3 \times 3[/math] matrices having real entries is a [math]GL_3(\mathbb{R})[/math]-set with the action [math]A \circ M = AM[/math]. That is, the matrix [math]A \in GL_3(\mathbb{R})[/math] acts on the matrix [math]M \in M_3[/math] to give the matrix multiplication [math]AM[/math].

What exactly is this question asking? I don't see how to answer it beyond "both are sets of 3x3 matrices with real elements, so matrix multiplication is obviously defined for all of them, because they're squares of the same dimension."

>>9446638
Read the definition of a group action. Verify that all properties hold. It's fairly simple but not that simple.

>>9446638
You have to prove that for all [math] M \in M_3 [/math] and [math]A, B\in GL_3(\mathbb{R})[/math]:
[eqn] I \circ M = M [/eqn]
and
[eqn] (AB) \circ M = A \circ (B \circ M) [/eqn]

>>9446646
>>9446651
ty anons

Question for medfags, what happens when you fuck up and accidentally hurt a patient, eg. when taking blood? Repercussions? Lawsuits? I'm not currently in a position where I have to do IV stuff but I may have to one day so just curious.

>>9446526
What do you mean?
The concept is useful, yes and it aligns with experimental results.

Its not any less real than kinetic energy

>>9446582
Does mass actually exist?

So is pretty much every high functioning student in grad school on drugs or am i just a pussy? I dont understand how my peers are turned up to 11 all the time. They consume and regurgitate information as easily as they breathe

>>9446669
Some definitely are, but don't be one of them.

>>9442805
i just started studying calculus and it's piss easy. will it get harder after derivatives and integrals?

>>9446744
Calculus requires a really high intelligence level to even begin to grasp. Seems like you're one of the gifted ones.

>>9446800
>Calculus requires a really high intelligence level to even begin to grasp.
I am pretty sure that you can make elementary school students grasp basic calculus stuff dude...

>>9446800
Kek. Brainlet detected

>>9446800
i sense irony

how legit is this paper?

are those equations just plug and play that engineers use or did the author actually derived them?

>>9446871
https://www.researchgate.net/publication/322530755_Analysis_and_Qualitative_Effects_of_Large_Breasts_on_Aerodynamic_Performance_and_Wake_of_a_Miss_Kobayashi%27s_Dragon_Maid_Character?channel=doi&linkId=5a5ef35a458515c03ee11245&showFulltext=true

the link, fuck im retarded

>>9446822
If they're some really bright students, then sure.

>>9442805
why does f=ma and not mv

>>9446668

Yep

>>9446871
This is fairly fundamental stuff. I mean you just plug in a model into a NS-solver like fluent and check the output.

Nothing spectacular.

>>9446887

Because that isnt Galilean invariant, sweetheart

Common sense tells me x3=10 and x1 and x2 = 0
with the minimum value being -10
this is worth 14% of a paper though so am I missing a chunk of the problem?
Also how to formally state my reasoning?

>>9446887
Because if a body receives no force, then its velocity remains constant.
If it were f=mv, then that would mean that the bigger the speed, the bigger the force.

Prove that the ring of Gaussian integers is an Euclidean ring.

Book gives a somewhat heuristic proof, but there is a step which I don't understand:

Let [math]x=1+i[/math],[math] y=2+3i[/math], [math]xy^{-1}=s+ti[/math] and [math]c+di[/math] be such that [math]\mid c-s \mid \leq 1/2[/math] and [math]\mid d - t\mid \leq 1/2[/math]. Now write x=y(c+di)+r. Then:

[math]N(r) = N[x-y(c+di)] \\= N[x-y(s+ti)+y(s+ti)-y(c+di)] \\= N[y(s-c)+(t-d)i](1)[/math] (This is the part I don't get it, what happened here?)

The proof then concludes with:
[math](1) \leq 1/2N(y) < N(y)[/math]

Hence the ring is euclidean since it satisifies the condition N(r) < N(y).

>>9446992
Woops, the part I don't get it is how (1) came from the previous expression.

>>9446996
>Woops, the part I don't get it is how (1) came from the previous expression.
It doesn't, it should be:
x-y(s+ti)+y(s+ti)-y(c+di) =
y(s+ti)-y(c+di) =
y[(s-c)+(t-d)i]

which is consistent with the equality seen here:
https://en.wikipedia.org/wiki/Gaussian_integer#Euclidean_division

Prove that [math]S=\{ x+y\sqrt[3] 3 + z\sqrt[3] 9, x,y,z \in \mathbb{Q} \}[/math] is a subfield of R.

I know that all the other properties of a field are obviously in this case, so all it's left to show is that the inverse is [math]\frac{x^2-3yz+3z^2-xy\sqrt[3] 3 + y^2 - xz\sqrt[3] 9}{x^3+3y^3+9z^3-9xyz}[/math] as stated in the book, however I can't reach this by myself. What algebra trick am I missing here?

>>9446996
Nevermind, got it. Wasn't paying enough attention.

>>9447021
>so all it's left to show is that the inverse is ................. as stated in the book
Why do you think the book stated the inverse?

>>9447032
I mean it's in the answer.

How do I prove
[eqn] s_{2^{n+1}-1} \leq t_{n}[/eqn]
for all [math]n\geq 0[/math], if [math]s_{n} = a_{1}+\dots a_{n}[/math] (defined for all [math]n\geq 1[/math]) and [math]t_{n} = a_{1}+2a_{2}+4a_{4} + \dots + 2^{n}a_{2^{n}}[/math] (defined for all [math]n\geq 0[/math]? Is induction the best way to prove this, or can I use some fact about series that would simplify this?

>>9447052
additional information: [math]\sum a_{n}[/math] is decreasing, nonnegative terms.

>>9447052
>Is induction the best way to prove this
Yes.

>>9447066
Is it fair to say [math]s_{2^{k+2}-1} \leq s_{2^{k+1}-1} [/math] ? The indices's on the LHS are growing faster than the RHS and we're decreasing.

>>9447021
>so all it's left to show is that the inverse is [math]\frac{x^2-3yz+3z^2-xy\sqrt[3] 3 + y^2 - xz\sqrt[3] 9}{x^3+3y^3+9z^3-9xyz}[/math] as stated in the book


Do you mean [math]\frac{x^2-3yz+(3z^2-xy)\sqrt[3] 3 + (y^2 - xz)\sqrt[3] 9}{x^3+3y^3+9z^3-9xyz}[/math]?

>>9447021
Also what you do:
1) Write (x+y*3(1/3)+z*9(1/3))^(-1) = a+b*3(1/3)+z*9^(1/3)
2) Multiply both sides by x+y*3(1/3)+z*9(1/3)
3) Group terms so that you have 1 = something + something*3(1/3)+something*9^(1/3)
4) Use linear algebra to solve for a, b and c
5) You get what's shown here >>9447085

>>9447085
Yes, thanks for correcting that. Got any clue as to how to reach that?

>>9447079
>Is it fair to say s2k+2−1≤s2k+1−1 ?
I don't think so, there's more terms on the left hand side.

>>9447093
but wouldn't decreasing ensure this?

>>9447093
oh shit, never mind I think I see what you mean.

>>9447093
>>9447101
yeah, I'm a bit lost here.

>>9447104
>yeah, I'm a bit lost here.
Write out what each of those are equal to, all the summands on the right hand side are on the left hand side too, but then there's extra terms on the left hand side (which are non-negative), so the inequality can't hold.

>>9447106
Yes, I see this now. But now I'm back to the drawing board. How should I proceed.

[math]\{ a,b \in $\mathbb{R}$ \vert a,b \neq 0 \}
Find real numbers c and d such that
$\frac{1}{a + bi} = c + di$

Evidence:
$\frac{1}{a} + \frac{1}{bi} = c + di$
By linearity: $c = \frac{1}{a}$ and $d = \frac{1}{d}i$
[\math]

Is this valid evidence or am I missing the point?

>>9447115
>How should I proceed.
To show that s_{2^{n+1}-1} <= t_n implies s_{2^(n+2)-1} <= t_{n+1}:

Assume s_{2^{n+1}-1} <= t_n.

sum_{i=0}^{2^{n+1}-1} a_i <= sum_{i=0}^n (2^i)a_{2^i}

a_{2^(n+1)}+...+a_{2^(n+2)-1} + sum_{i=0}^{2^{n+1}-1} a_i <= a_{2^(n+1)}+...+a_{2^(n+2)-1} + sum_{i=0}^n (2^i)a_{2^i}

sum_{i=0}^{2^{n+2}-1} a_i <= a_{2^(n+1)}+...+a_{2^(n+2)-1} + sum_{i=0}^n (2^i)a_{2^i}

s_{2^{n+2}-1} <= a_{2^(n+1)} + ... + a_{2^(n+2)-1} + sum_{i=0}^n (2^i)a_{2^i}
since a_n is decreasing:
s_{2^{n+2}-1} <= a_{2^(n+1)} + ... + a_{2^(n+1)} + sum_{i=0}^n (2^i)a_{2^i}

s_{2^{n+2}-1} <= 2^(n+1) * a_{2^(n+1)} + sum_{i=0}^n (2^i)a_{2^i}

s_{2^{n+2}-1} <= sum_{i=0}^{n+1} (2^i)a_{2^i}

s_{2^{n+2}-1} <= t_{n+1}

>>9447121
>$\frac{1}{a} + \frac{1}{bi} = c + di$
Wrong.

>>9447131
How? I'm just separating the fraction apart

>>9447134
>I'm just separating the fraction apart
No you're not.

>>9447128
god damn anon, thanks. I'm not used to induction on series and I was considering suicide.

>>9447137
...okay, so what should I be doing instead?

>>9447090
>4) Use linear algebra to solve for a,b and c

Uh, how exactly?

>>9447153
>Uh, how exactly?
1 = something + something*3(1/3)+something*9^(1/3)
gives three equalities
1 = the first something
0 = the something in front of 3^(1/3)
0 = the something in front of 9^(1/3)

these right hand sides are all linear in a,b,c so you set up the augmented matrix in the basis a,b,c (something like {{x,3z,3y,1}. {y,x,3z,0},{z,y,x,0}}) and row reduce to solve for a,b,c.

>>9442805
Not particularly related to science/math, but I don't know where else to post:
A friend of mine got me a print+digital subscription to NationalGeographic, and I was wondering when the print magazines usually get sent out (I can't find any information on this online)

I'm doing [math] \int \sqrt{4-x^2} \:dx [/math] and subbing in 2cosu at the start, and I get a arccos(x/2) term at the end. The calculators online always sub in 2sinu instead and get an arcsin(x/2) term at the end. All my work seems to be right, does it matter which one you sub in?

>>9447121
>Find real numbers
>Is this valid evidence or am I missing the point?
No "evidence" for the existence of real numbers can be valid.

>>9447192
Well I don't know what the fuck to call it, certainly not "proof"

>>9447198
No proof of their existence exists either, since there is a proof of their non-existence.

>>9447202
Yes, I know, that's why I specifically said "certainly not proof".

>>9447160
Ah, I see it now. Thanks for the help.

What's the name of the property where
[math]$ 4x = 16 $
$ 5x = 20 $
So
$ 4*20 = 5*16 $[\math]
?

>>9447202
>there is a proof of their non-existence
Show it to me.

>inb4 hand-wavy bullshit based on the assumption that numbers are sequences of digits

Discrete math/proofs question

>is it possible that X is a tautology even though {X,Y,Z} is inconsistent

my answer was Yes for this one.

>Is it possible that x or y or z is a tautilogy even though {x,y,z} is inconsistent

this is true right? because there can never be a case where they are all false as the set is inconsistent.

So I got a Computer Programming AS/Cert to find a litle job to pay the bills and I'm kinda bored,what's a good major to apply this to that isn't CS?

>>9446459
bumping this

>>9447365
It's not a property, it's just variable substitution.
20x = 20x, so 4*(5x) = 5*(4x), i.e. 4*20=5*16.
Of course this only works if x happens to actually be the same number in both cases, like here.

>>9446459
that looks good, except f(x,y,z)=c will naturally only eliminate 1 variable and still make for a 2 dimensional surface. Your solution would allow x to be 9001. So x=1/(2pi) will be the other constraint and I think then you're good.
As a sanity check, plug in your r_x(t) and r_y(t) and r_z(t) into f and see that it's indeed 1 for each t.

Can someone point me in the right direction here? We haven't even learned this yet.

>>9447523
>Can someone point me in the right direction here?
What have you tried?

>>9447524
Well I think I know how to prove the result by saying that the mth element of T is equal to a combination of previous elements, i.e Wm = W1 + W2 and therefore would be larger than S and also be linearly dependent. But I don't know how to relate that to proving that k = m

What are some good questions to ask a cardiologist?

I'm working for one while I'm applying to med school and every other week we sit down and I ask him any questions and after a few of these I'm running seriously low on shit to ask about.

>>9442975
May I ask what software are you using to annotate your notes

>>9447548
In terms of the career or the field itself?

>>9447548
Is it true that the heart wants what it wa-a-a-a-a-a-a-a-a-ants?

>>9442805
https://www.gsb.stanford.edu/faculty-research/publications/deep-neural-networks-are-more-accurate-humans-detecting-sexual
Is there any useable implementation of this (like a website where you upload a picture and get a result)?

>>9447143
1/(a+bi) is not 1/a + 1/(bi). Try multiplying numerator and denominator by the complex conjugate of a+bi, namely a-bi

>>9443210
Kill yourself, honestly. you pathetic scum male in denial cunt brainlet. Yes you triggered me

>>9447640
>Kill yourself, honestly. you pathetic scum male in denial cunt brainlet. Yes you triggered me
How are you?

>>9447644
Are you the depressed tranny whore from the math discord?

>>9447646
>Are you the depressed tranny whore from the math discord?
Can you be more specific?

>>9447624
Up to now I've only been asking about the field itself.

Why isnt there a career general thread?

Anyway, I have the option of going to medical physics or nuclear research for grad school. I could also do optics or solid state on a fellowship with tuition paid for.

Any brainlets wanna determine my future for me?

>>9448055
>Why isnt there a career general thread?
Did you read the sticky?

>>9448057
the sticky is retarded. science and math are both professions so it would make sense to talk about the career aspects.

>>9448086
>science and math are both professions so it would make sense to talk about the career aspects.
Scientists and mathematicians have to eat, should food threads be allowed on /sci/?

Hey /sci/ I'm kinda a brainlet and I'm finishing my last year of highschool. I was thinking of getting a bachelor's in computer information systems, since my dad wants me to into business and I want to go into technology. The thing is I'm not sure if I should minor in mathematics, I'm not very good at it but I love how challenging it is. Any advice, I'll send the program I was thinking of if anyone's interested.

>>9448101
>computer information systems

This is garbage.

>>9448109
>This is garbage.
How can a meaningless notion be garbage?

So I have this sphere modeled by [math]x^{2}+y^{2}+z^{2} = 6[/math] and the paraboloid that's passing through it is [math]z=4-x^{2}-y^{2}[/math] . How would I go about finding the parametric equations of the boundary curves of the sphere? I

>>9448581
With a system of both equations.

If [math]ap = bq[/math], where [math]a,p,b,q = \mathbb{Z}[/math] and [math]GCD(a,b) = 1[/math], does this imply that [math]a[/math] will always share prime factors with [math]q[/math]? I'm assuming that (by Euclid's lemma), since [math]a \not| b[/math], this must mean that [math]a|q[/math].

>>9448101
>"The Bachelor of Computer Information Systems (abbreviated BSc CIS) is an undergraduate or bachelor's degree that focuses on practical applications of technology to support organizations while adding value to their offerings."
>"adding value to their offerings"

What does this term even mean? It's meaningless language, and it points to the fact that this "field" doesn't have any value. At all.

t. MD/PhD-student

>>9446685
>>9446669

fuck that, get on rita for a couple of years, get good grades.

>>9448581
Like this.

How do I get into Bibliotik? Libgen doesn't have the books I'm looking for. Also, seconding the anon from a few days ago, what are good books on neural networks? I've already read the ones above and sat through the lectures, except the ongoing one.

Super easy question coming through
If I have a circuit with a branch that has a voltage generator, a current generator and a resistance, and some other parallel branches. Can I use Milman's theorem? How would that work I should have to ignore the voltage generator and the resistance right?

>>9448753
I'm not completely familiar with millman's theorem, but you can convert a voltage source to a current source and vice versa as long as you know the internal resistance by ohm's law [math] V_s = I_s R_{int} [/math] internal resistance stays the same but in a voltage source the resistance is in series with the source and with a current source it is in parallel with the source

Taking a look at millman's theorem, that is essentially what is being done, turning voltage or current sources into the other and combining them then turning it back into the original source type and rearranging the formula to make it pretty

my math is bad as fuck, where should I start to learn it again?

What am I doing wrong in this latex? I'm trying to make it so that my list has the form
a)
b)
c)

But for some reason it's not working

>>9448938
Try [a)] instead of [label=...]

>>9442805
For [math]x^8-17x^4+16=0[/math], I got 4 answers. 1,-1,2,-2. The book also lists the solutions i, -i ,2i, and -2i. I don't understand why those are answers and how they got that.

>>9447523
bumping for help

>>9449015
ax^2+bx+cx^0=0 is quadratic
you can make your expression quadratic
All the terms are to the rght powers

>>9449015
When you factor the expression you get (x-1)(x+1)(x+2)(x-2), which would give you your answers, as well as (x^2+1) and (x^2+4). setting those equal to 0 gives sqrt(-4) and sqrt(-1), which would give i,-i, 2i, and -2i

>>9448945
I'm a retard... found out that my problem was that I wasn't importing the correct package

Could it be that the giant black hole in the middle of the milkyway one day decides to 'do' something and everything just vanishes, essentially fucking us? Without warning or anything. I mean we don 't know enough about it to rule it out right?

>>9448650
>If ap=bq, where a,p,b,q=Z and GCD(a,b)=1, does this imply that a will always share prime factors with q?
No. Consider a=b=1 and p=q=2.

>>9448747
>neural networks
not science or math

>>9449286
It's both actually, but okay.

>>9448930
Depends on where you level is at, but I'm pretty sure the sticky has guides and free online classes, like khan academy and such.

does euclid's 1st proposition require an additional postulate in his book the elements?
i mean, how does he know 2 circles with centers as the extremeties of a straight line and radii that line intersect?
also, what would be the approach to proving more propositions if that were impossible?

>>9443136
qBittorrent with the search function enabled.

>>9448581
l-lewd

What are the best physics books for a math student who was completed pretty much all undergraduate level material? Can I skip to grad level physics books or should I build up easier physics knowledge first?

>>9442805
will i get v& using libgen?

>>9449545
>will i get v& using libgen?
Only if you live in a third world country.

this is my first time using the circuitiks package for latex. actually it's essentially my first time using latex too. and also my first time doing anything with circuits (it's for a class).

does this look retarded or do you think I could just turn it in like this? my latex code is fucking retarded and a mess so I only want to fuck with it more if I have to.
we were allowed to use whatever program we wanted to draw diagrams so I chose latex because I'm a tryhard.

>>9449430
All the math physics grads I've spoken to that skipped to grad level physics books regretted not building up intuition with undergrad books.

>>9444905
If the question is given in this format, I would just do the following:

1) Scrap the one options that clearly don't make any sense at first sight I mean things like an upper limit proving divergence or something like that.

2) Quickly check if the first part of the expression (before the and) is true for the first remaining option. If not scrap and go on to the next option.

3) Quickly check if the last part of the expression (after the and) is true for the first remaining option. Otherwise scrap.

Keep repeating 2 and 3 until you both parts of an option are correct.


If you don't know how to verify the first part: just simplify until it's trivial.

>>9446963

Express x3 in function of x1 and x2, then define y to be the given formula above

You can now look at the problems like a 2D surface in the 3D space spanned by x1,x2,y.

Now minimize y in function of x1 and x2. If you don't know how to do this last part I'm sure you didn't studied enough to be able to do this exercise yet.

>>9447021
It's a subset so all you have to do is show closure:
0/1: trivial
+/-: trivial
*: trivial
÷: Remember what you did to define dividing complex numbers? Do the same thing... twice.

>>9449430
This is generally a really bad idea.

So what is your goal? Do you want a job in physics? If so, youll be clueless on your jobsite if you skip undergrad material. The further up you go in physics, the less useful textbooks are because they essentially turn into reference books instead of books designed to be learned from.

Undergrad books arent as bad as they sound, theres no shame in reading them.

>>9449609
for the given limitations ofcourse!

so
x1>= 0
x2>=0

and because x3 = 10-x1-x2 >= 0
x1+x2<=10

What are those summer break research programs like? My uni has sent a few out and I'm just curious about it. What would it be like for someone who has no substantial knowledge?

>>9449567
Looks fine by me. The placement of Carry would be a bit goofy if it wasn't an output, but since it is and output it's fine.

>so I chose latex because I'm a tryhard.
I too made that "mistake". It's not really a mistake since you'll learn it and you'll definitely need it later. However I would personally suggest using faster WYSIWYG methods for smaller assignments.

How do you make this step?

>>9446744
>will it get harder after derivatives and integrals
kek, that's pre-calculus highschool shit.

>>9446800
topkek

Although, if you're talking about the general populus you're probably correct, but taking STEM people as the baseline I would never go as far as saying you have to be "gifted to even begin to grasp it".

Now that I think about it, all highschool kids here have to grasp the fundamental theorem of calculus to pass.

>>9449658
First expand the top formula. If you don't see it by then I will help you. But you gotta put some work in yourself first.

>>9448930
Do Khan Academy from where you get it until you understand calculus and linear algebra. I would consider that a good basic grasp on math for the average person.

It's impossible to fail because he goes through every step very slowly and explains the reasoning in detail at every step. If you didn't get a step, just rewind a bit and listen to his explanation slowly.

If he gets to slow for you at points, put youtube speed higher, you can always slow down on hard parts. If there a step you don't understand and he goes over it without explanation, that means that you don't understand a preceding video and have to finish that playlist first.

>>9446408
Isn't that logical? Where is the magnetic field strongest close by or far away from a magnet?

>>9449664

This isn't good advise. You can do it more quickly my simplifying the top formula.

Note that 4c^b^2 - (b^2 + c^2 - a^2)^2 is the difference of two squares. So you can write it as (2bc - b^2 - c^2 + a^2)(2bc + b^2 + c^2 - a^2).
But each of those terms in the parenthesis are also differences of two squares:

(-(b-c)^2 + a^2)((b+c)^2-a^2)

You can do it again.

(a - b + c)(a + b - c)(b+c-a)(b+c+a)

Done!

>>9449686
If someone post a question that they don't know the answer to, I believe in providing them with the general solution so that they at least always come to an answer. I personally believe that finding faster way for certain cases is a step you take only after you understand the basics. If Anon had given the correct answer and asked "is there a faster way to do this" it would be a different story ofcourse.

Just a different style of tutoring I guess.

>>9449697

But they are looking at something about Heron's formula, and are only asking us to help them through some algebra. "The basics" we'd be teaching them, after prompting them to expand the top formula, would just be some annoying algebra. You don't really learn much from doing that, do you? It's just a lot of work and doesn't help you understand Heron's formula.

>>9449664
I already made a few attempts, I always end up with this tough and always get stuck on how to expand it any further.

>>9449707
see
>>9449686

Turns out you can do it in three or four lines of algebra

>>9449638
It's supposed to be a learning experience for you. They don't care if you're already an expert in something; in fact, they usually expect you're not. They're more interested in your talent and resolve to actually get shit done.

>>9449706
I guess you're right, I wasn't really looking at what the formula was for. I was more worried about him not being able to find a solution at all.

But since he's probably studying for an exam for which this algebra is mostly irrelevant it's not the right time to focus on that.

>>9449686
Ah thanks I'll check it out right away.

>>9449722

To your credit, though, the only reason I can do it quickly myself is because I've banged my head against the wall doing horrible algebra many times before. Only practice can make you self-sufficient.

>>9447523
>>9449019
>>9447529

You already figured it out, you only have to connect the dots:

The vectors in a base are by definition independent so proving a base contains linearly dependent vectors is a contradiction. So when your proved (2) you proved k>=m. By making the exact same with k>m you again proof this leads to contradiction and thus k<=m. For both of these to be true k must be equal to m.


This is called a proof by contradiction. You assume that the opposite is true and when you then run into a contradiction, you know that the opposite is true.

let f [1,2] -> R, f(x)=-2x. Prove by definition that f is Riemann-Integrable.
I guess I've got to make two step functions h and g such that h<f<g.
I'm trying to fill the graph with rectangles which lenght is 1/n and height (k-1)/n, but those values won't ge me anywhere.

>>9442961
how?

>>9449820
Thank you. This is my first proof based course, and I am not used to this kind of thinking.

Can anyone help me with this problem?

>>9450132
>Can anyone help me with this problem?
What have you tried?

>>9450145
I tried integrating in respect to x first which nets me 1/2x^2sin(y^3+1) that i have to integrate in 3 and y thus 4.5sin(y^3+1) - (1/2y^2sin(y^3+1) and then I'm supposed to integrate that to y but I just don't know how.

>>9450157
>>9450145
actually integrating 4.5sin(y^3+1) - (1/2y^2sin(y^3+1) gets me -4.5cos(y^3+1) +1/6y^3cos(y^3+1) but then integrating in 3 and 0 doesn't give me the correct answer of −1/6cos(28) + 1/6 cos(1) so I'm doing something wrong, but I don't know what.

>>9450132
try drawing out the region that you are integrating over on a piece of paper, then determine what your limits of integration should be, it should be pretty clear what you are doing wrong

Can someone please give a mathematical definition for the "p-value"?
Googling for it just results into a bunch of unrigorous wordings for it.

>>9450216
lowest value of alpha for which H0 can be rejected

Is abstract algebra harder than adv calc?

>>9449567
Is that schizophrenia?

>>9450256
I think it's EE

>>9449567
Just use SPICE or Multisim you faggot

I have a question about Osmium. So it's the most dense thing on the planet, but according to wikipedia it's also brittle. I have a hard time wrapping my head around this. When I think about diamonds I think that they are very dense but also very hard. My understanding was that these two things were tied together. Exactly how brittle is Osmium? Saw you had a solid bar, could you snap it with your hand? Or break it by smashing it onto the ground?

Say you wanted to make a hammer out of something extremely hard and dense. If Osmium isn't the best element to make a hammer, what would be the best compromise? Diamond?

>>9450331
diamognd pickadxe

>>9450339
Is this because of my typo? I'm sorry, I haven't been getting a lot of sleep.

So I have to solve this equation [eqn]u_{yy} - \frac{1}{(2x+1)^2}u_{xx} - \frac{2}{(2x+1)^2}u_x = 0[/eqn]. I do as always, get its canonical form and do the rest. But just what the fuck am I supposed to do with this shit?
[eqn]v_{\xi \eta} - \frac{1}{(2x+1)^2}v_{\xi} + \frac{1}{(2x+1)^2}v_{\eta} = 0[/eqn]
where
[eqn]\xi(x,y) = y-x^2-x, \eta(x,y)=y+x^2+x[/eqn].

>>9450739
Sorry, the third term of the first equation should be cubed, not squared.

Should I just drop math if Im struggling in a proof class? I got all As up to adv calc/abs algebra. Math is my 2nd major. I need 3 more theory classes for the major but dont want to tank my gpa. Is there hope for a brainlet to get an A in theor math or nah

>>9449390
does anybody know?

>>9450341
density doesn't measure the material's strength or resistance, only how well its atoms can occupy empty space
diamond is very strong because all carbon atoms are in a close to perfect lattice, surrounded by another 4 C atoms each in a very stable conformation
the energy required to displace or break the lattice is enormous, hence diamond's hardness

>>9450776
So say you had something that could dissolve objects, like an acid that could even chew through diamond. Would the osmium dissolve slower because of it's density or the diamond because it's harder?

>>9450745
>Should I just drop math if Im struggling in a proof class?
define "proof class"

>>9450782
density doesn't measure how fast a material dissolves in an acid, either

>>9450805
Well, shit. Really? i'm having a hard time understanding this

>>9450812
density measures how much mass the material has per unit volume. why do you keep trying to make it to be something else?

>>9450813
I'm just trying to figure out how quickly one would dissolve. I'll spill the beans and say I'm trying to write a story about anti-matter, would a super dense object be better for handling/transporting it or a super hard object?

What are some of the most 'complete'/extensive books in Linear Algebra, Real Analysis. NOT for self teaching!

For example: Most LinAlg books just go from basic algebra to vector spaces, maybe direct sums and dual spaces to linear transofrmations, determinants, eigenvalues and -vectors and finish off with (S)O, euclidian/complex vectorspaces, and modules.
A few touch subjects like multilinear algebra and tensor algebra for example.
And none I know of touch topics like matrix bundles, or 2/3/4 (unsolved) subspace problems.

Another example: Blue and Green Rudins are considered very terse but extensive books on basic real analysis but they lack measure theory/good chapter(s) about lebesque integrals.
I'd consider Tao's Analysis book to be quite nice, too, but some of his definitions and proofs are plain ugly like everything regarding set theory, axiom of choice and stuff like that.

>>9450825
Oh, and I know that complete/extensive if somewhat super stupid to ask, cause then the only answers would be Nicolas Bourbaki + all math papers published every...
Extensive in the sense that a LOT regarding making progress is being proven very precisly and thing interesting enough get there own sections (for example reordering series so they converge/diverge).

>>9450825
>matrix bundles
what do you mean by this ? principal bundles ?

>>9450825
>>9450828
you're kind of asking for a complete, modern compendium on linear algebra and real analysis. as you said, bourbaki is the right answer...

you can also try graduate level books with fairly complete topics and exposition. roman's "advanced linear algebra" has some interesting things on that direction, and folland's "real analysis" has quite the complete selection of topics. that's probably what you're after

>>9450838
>>>9450745
my bad, it is called "Matrizenbüschel" in German (not bündel = bundle).
To be more precise the problem about classifications of matrix pencil is the (open) problem.

There is a statistical tool that it’s used to work with the chances of an event happening when the only (?) variable is what kind of event happened before in that sequence or whether it happened or not.
This isn’t a super obscure piece of trivia, because I know that it’s widely used in search algorithms, for example, but I can’t remember the name of it.
I think that this tool/method/whatever is commonly referred as a x’s sequence, where x is the name of the man who developed this method.
Does anyone know the name of it?

>>9450868
Markov, maybe? I don't know anything about the topic, mind you, but the name bells a ring.

>>9451015
YES, that's what I was thinking about.
Thank you so much for your time.

>>9451520
>>9451520
NEW
>>9451520
>>9451520

>>9450825
>What are some of the most 'complete'/extensive books in Linear Algebra

Linear Algebra and Geometry by Kostrikin and Manin (Physics flavored)
Linear Algebra and Its Applications by Lax (Analysis flavored)
Advanced Linear Algebra by Roman (Abstract Algebra flavored)
Matrix Computations by Golub and Van Loan (Numerical flavored)
"Matrix Analysis" and "Topics in Matrix Analysis" by Horn
"Linear Algebra" and "Multilinear Algebra" by Greub (The book)

>Real Analysis
You don't know the OP?
http://math.caltech.edu/simon/ComprehensiveCoursePreview.html