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/sci/ - Science & Math

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11120908 No.11120908 [Reply] [Original] [archived.moe]

Formerly >>11100698
Why the hell did you lads actually wait for me edition.

>> No.11120914 [DELETED] 

I was tempted to start one. Didn't know if you'd mind~

>> No.11120997
File: 138 KB, 712x1104, IMG_1426.jpg [View same] [iqdb] [saucenao] [google] [report]

Asking again but more specific now to see if I get an answer this time.

You guys know what the symbol below the valve means (it's a P&ID diagram btw)? It looks like a check valve but I also have the irl photos of the sistem and I don't see anything there.

>> No.11121001
File: 272 KB, 604x900, __patchouli_knowledge_touhou_drawn_by_maguro_mawaru_sushi__afae8c03397e57bd75620bca28eb7a72.png [View same] [iqdb] [saucenao] [google] [report]

Is there any archive that pops up a posting window like 4chan does? I had to actually tally this shit up by copying and pasting to notepad.
There are probably some formatting errors, but catching them without just posting would be a huge pain.
I obviously wouldn't.

Unanswered questions from the previous thread:
Maths questions:
>>11109144 [I still need those recs.]

Physics questions:

Chemistry questions:

Biology questions:

/g/ questions:
>>11114863 [Quantum computing.]

Stupid questions:
>>11102675 [I have absolutely no idea where this goes.]

>> No.11121009

How can blood pressure medicines work without just killing you? Doesn't the body only increase the pressure in its veins when it NEEDS that pressure to be higher?

>> No.11121054

I imagine they can be continuously elevated beyond the point it's considered healthy due to stress, bad diet, etc. My father regularly reports +180/+120 when he's had a morning where things didn't exactly go his way.

>> No.11121055

The inertia of the water just allows the coke+mentos reaction to build up more pressure before it starts shooting out its contents. The higher pressure equals more potential energy stored inside and a higher exhaust velocity of the coke, making it go higher.

>> No.11121074 [DELETED] 

pretty sure it means there are two check valves in series there

>> No.11121120
File: 98 KB, 571x315, engcuck.png [View same] [iqdb] [saucenao] [google] [report]

so anyone have any suggestions on how to start this problem?

>> No.11121131

If you're low IQ, is it still possible due to crossing over, independent assortment and random fertilization to conceive a high IQ child?

>> No.11121141
File: 90 KB, 516x380, WhatsApp Image 2019-11-01 at 11.39.36 AM.jpg [View same] [iqdb] [saucenao] [google] [report]

Yeah the symbol looks similar, but I don't see them irl.

>> No.11121158

i want to cuddle with patchy

>> No.11121182

will the 200,000,000 Trees planted by Mr. Beast do anything ?

>> No.11121193

gauss' mother was illiterate and his father wasn't much better apparently

>> No.11121214 [DELETED] 

Yes, it will do "something"

>> No.11121253

For stochastic processes, or random processes, does it make sense to vary more than one parameter at a time, i.e. amplitude and phase for a sinusoidal signal?
or would it make more sense to just vary amplitude?

>> No.11121519

How do you know when to convert from degrees to radians?

>> No.11121520 [DELETED] 

most formulas require angle to be in units of radians

>> No.11121522 [DELETED] 

if an answer states it wants the answer in one or the other. also typically on diagrams it's better to use degrees

>> No.11121527

You almost exclusively just use radians for calculations, although how you present your results depends on the particular requirements and ultimately your choice. Specifically, if for example I'm just trying to describe a system or an image geometrically I'd probably use degrees.

>> No.11121607

How do I prove that a function has a global minimum or maximum in all of its domain without using derivatives? I'm talking specifically about e^(-x^2)

>> No.11121682

/an/ here, they say they're collaborating with the Arbor Day Foundation to plant native trees species on habitats suitable for restoration across multiple countries. There is some debate about whether the foundation will manage the sites to ensure that secondary succession will properly take place and not just abandon the sites for deer and shit to strip the understory before it can grow properly. Other than that, these areas they say they'll plant on are already ecologically degraded (like mining sites) so its a net positive trying to restore it.
>inb4 China and Brazil destroy more natural land so why bother restoring already degraded habitats on other fucking continents.

>> No.11121694 [DELETED] 

it's only 20million, which is 0.000666% of the total trees now, so sure it might do something, but not much.

>> No.11121790

Is the echo a manifestation of sound waves being reflected?

>> No.11121819
File: 25 KB, 770x332, helppls.png [View same] [iqdb] [saucenao] [google] [report]

How does someone find the appropriate characteristic equation for the expression above?
What can I search for to refresh on that sort of thing?

>> No.11122011

e^x is strictly monotonic increasing, so a global minimum/maximum of f(x) is also a global minimum/maximum of e^f(x). -x^2 has a global maximum at x=0 (it's zero at x=0 and negative everywhere else).

>> No.11122262 [DELETED] 

Basically yes

>> No.11122724

Chemistry noob here.
I need to clean a platinum crucible that has some manganese tungsten oxide (MnWO4) on it.
What chemical should I use to dissolve it?
If you have an idea what acid I should use please also tell me the concentration/temperature needed.

>> No.11122746
File: 1 KB, 123x110, 2.jpg [View same] [iqdb] [saucenao] [google] [report]

what's this symbol called?

>> No.11122775

How would I go about for sketching sinc(200pit)sinc(2100pit)?
Fourier transform gives me (1/200)*rect(f/200)*(1/2100)*rect(f/2100)
Don't really know where to go from here or how to even carry out this multiplication

>> No.11122853

Lemma 1: Let g be a strictly increasing function. Then x is an extremum for f if and only if x is an extremum (of the same type) for g composed with f.
Proof: exercise

Lemma 2: The function -x^2 has a single local maximum, occuring at x = 0. It is also its global maximum.
Proof: High school math.

Now apply lemma 1 and lemma 2 for f(x) = -x^2 and g(y) = e^y

>> No.11122868

Boyle's law says PV = constant

But what if I add a few molecules in a container? The pressure will increase but the volume will stay the same. How does it work?

>> No.11122917

That's incomplete, Boyle's law says that PV remains unchanged in a closed system.
If you add molecules then the system isn't closed anymore, so there's no reason Boyle's law should still hold.

>> No.11122919

Also meant for >>11122868, I don't know why the fuck I linked that other post.

>> No.11122957

Ah thanks

>> No.11123156

You want the ideal gas law: PV/nT=R, where P=pressure, V=volume, n=quantity (number of molecules), T=temperature, R=ideal gas constant (= product of Boltzmann constant and Avogadro constant).

If you increase n while keeping V and T constant, P increases in proportion.

Boyle's law: P∝1/V => PV∝1
Charles's law: V∝T => V/T∝1
Avogadro's law: V∝n => V/n∝1
Gay-Lussac's law: P∝T => P/T∝1

The ideal gas law combines the above into PV∝nT => PV/nT∝1

>> No.11123216

For a given number of molecules/mass of gas.

>> No.11123222

Denotes a binary relation. Seems to be used mostly in set theory and is read as "corresponds to"

>> No.11123397
File: 93 KB, 867x405, file.png [View same] [iqdb] [saucenao] [google] [report]

can someone explain this?

>> No.11123448

Two dice are rolled. The roller says at least one dice rolled a 6. What is the probability that the sum of both rolls is 7?
My answer is 1/6 here because you need a 1 to get a sum of 7.

Now what if at least one dice rolled a 5. What is the probability the sum is 7?
Again my answer is 1/6 because you need a 2 to get a sum of 7.

Am I doing something wrong here? The answers seem too obvious and I am questioning myself.

>> No.11123549

Interesting. I don't know.
Hübnerite is apparently a good source of tungsten, so look up how it's refined.
Conc. hydrochloric acid sounds like your best bet, since MnCl2 seems the most soluble, and similar to the refining of CaWO4 to make tungstic acid.
Also try concentrated lye, which is used in wolframite (mix of Fe and Mn tungstates) processing

>> No.11123607

If the person you're talking to has completed high school math

>> No.11123612

see angles in terms of pi, you’re using radians, see angle that’s quite large with numerical representation that’s quite small, its radians, doing physics problem? probably degrees

>> No.11123783
File: 489 KB, 961x1000, curled.png [View same] [iqdb] [saucenao] [google] [report]

Illegible question, try rewriting in a clear fashion.
[math]\frac{ \partial ^2 u}{\partial x^2} - 2 \frac{\partial ^2 u}{ \partial x \partial y} + \frac{ \partial ^2 u}{\partial y^2}= (\frac{ \partial ^2 }{\partial x^2} - 2 \frac{\partial}{ \partial x \partial y} + \frac{ \partial}{\partial y^2}) u=0[/math].
Now you've got a nice operator that indicates the direction in which u doesn't change, and you'll multiply it by [math] \partial y^2 [/math] and cancel stuff out, because we can't have fractions with empty numerators.

As always for problems in calc and DEs, in doubt, turn your brain off and think "what would a physicist do?"
There are 36 possible results for throwing two dice. There are 11 cases where one is 6 (6 where the first one is 6, 6 where the second one is, and we remove the double). Out of those eleven, there are two where the sum is 7. That gives 2/11.
Same technique works for five.

>> No.11124377

how do i set up a triple integral to find the volume of a paraboloid between two planes using spherical coordinates? really just, how do i convert a paraboloid to spherical coordinates?

>> No.11124498

I am looking into the theory of linear regression with random variables instead of having samples.

When we have m samples with n features then linear regression becomes

Where X is a m by n+1(it has a 1 insert for the constant coefficient) matrix.

But what about the case where we don't a sample data set but instead we have information about the regressors?
Like their variance and variance, there is a theory on how to do this but I cant find it and google only returns the first model.

Can someone point me to a specific name or book?

>> No.11124557

> how do i convert a paraboloid to spherical coordinates?
Put the focus at the origin; then it's just
r = r*cos(φ)+d => r = d/(1-cos(φ))
where d is the distance of the focus from the directrix.

>> No.11124822

Let's say I have some odd shaped region given by two functions. I'm curious if there is some "standardized" way to coordinate transform this region into a circle and compute the area from there. I can definitely just compute the area of the region and then solve for the radius of the circle but I'm curious about trying to get this whole "coordinate transformation" to click with me.

>> No.11125045

Thanks, yesterday I tried it with hot diluted HNO3 and it didn't seem to do anything, so today I decided to put it in an oven with some Na2WO4 and heat it to 1100°C for a few hours, since that was used as a solvent for the hübnerite for high temperature solution crystal growth in the first place.
Hope it doesn't fuck up my crucible.
If it doesn't clean it I'll just reuse the crucible as is.

>> No.11125188


>> No.11125432


>> No.11125462

In general, an arbitrary shape cannot be linearly transformed into a circle

>> No.11125467
File: 21 KB, 575x241, SumatraPDF_2019-11-07_20-26-21.png [View same] [iqdb] [saucenao] [google] [report]

i don't get it. what says that i'm allowed to pull the minus sign outside the parentheses like that in the last equation?

>> No.11125471

(-A) = (-1×A) = -1(A) = -(A)
proof: trivial

I hate pure math so much

>> No.11125474

I don't think he's talking about linear transformation

>> No.11125478

It reads
(-a)b = -(ab)
right there

>> No.11125487

it would be easy if it said -((-1)(-1)) but -(ab)=(-1)(-1) is just confusing

>> No.11125514

Yeah. Any book that spends the first couple chapter sperging out of elementary definitions like what "A<B" means or "-A" means is bullshit.

>> No.11125598


>> No.11125683


>> No.11125705


>> No.11125960
File: 1 KB, 139x79, firefox_2019-11-07_23-04-40.png [View same] [iqdb] [saucenao] [google] [report]

How can I show that the limit does not exist?

>> No.11126032

How do you cope with being one of the lower IQ individuals in the family? I find it hard to believe that I can actually get gud at math when I'm still in statistics and my younger sister is in calculus! Blackpill if there ever was one.

>> No.11126038

Sign of denominator for x<0 and x>0.

>> No.11126042

Thought it said x instead of |x|. Never mind.

>> No.11126048

I'm a total retard. Just show that the numerator doesn't go to zero but the denominator does. Basic HS math.

>> No.11126065

How long does it take for the body to deal with sugar?
Let us start with a soda's worth.

>> No.11126130

what's the downside to very high voltage batteries? EVs these days have 400V batteries but for charging to be even faster, the voltages need to be in the ranges of 800+ for charge times (almost) comparable to ICE refueling
what's stopping manufacturers from doing this? Is it unsafe? hard to make? Please explain like you would to a child, thanks.

>> No.11126546


>> No.11126630

To increase energy capacity, you can connect cells in parallel (low voltage, high current) or in series (high voltage, low current).

The parallel case typically requires load balancing: ensuring that the current is divided equally amongst cells, which requires some amount of circuitry per cell. And if you have hundreds of them, that's going to cost. An added factor is that you need thick cables to carry thousands of amps.

With the serial case, the same current flows through each cell in the chain; there's no need to actively balance them. And you don't need thick cables.

In practice, you use a combination of the two: multiple cells wired in series to produce a high-voltage battery, then a few such batteries wired in parallel, with a regulator circuit for each battery. The number of batteries versus the number of cells per battery will be a trade-off of several factors.

The limiting factor on voltage is partially safety, and partially the cost and efficiency of the electronics. Components which can handle significantly more than a few hundred volts are somewhat niche items, so compared to more mainstream components they don't have the same economies of scale (making them more expensive), nor have they had the same amount of R&D (making them less efficient).

>> No.11127002
File: 29 KB, 452x678, he loves it.jpg [View same] [iqdb] [saucenao] [google] [report]

Hey anyone here do cognitive neuroscience? I participated in a cognitive task experiment recently using an EEG, and the experimenter said that i have an unusual amount of activity at electrode T7 and TP9 ((?) it could be TP7 and T9, i cant remember exactly) even when not doing the tasks, which they hadn't seen in the other participants. I assume there is an international standard for EEG caps, but i haven't been able to find what brain regions + functions relate to what electrode placements. So if there is anyone here who does work with EEGs or knows about them, can you let me know what these electrodes were recording? Broadly speaking it seems like the left temporal lobe, but i don't know anything more than that.

>> No.11127077

We dont need to exceed escape velocity to get outof earth if we have constant acceleration. Then can we escape event horizon that way?

>> No.11127139

What determines how much metabolic energy the brain can access over the course of a single day?

>> No.11127399

Can daylight saving time screw up your circadian rhythm? I usually fall asleep at the same time every day around 10:30 or so and wake up at between 5:00 to 5:30. For the last few days I've been waking up between 4 and 4:30 and been finding it hard to fall asleep quickly for that last hour. I've never been as disciplined about my sleep schedule as I have this year so I wouldn't have noticed if it's affected me before.

>> No.11127484

Guys I wanna make small vacuum chamber to remove air bubbles form epoxy mixture.
Now i dont know these things well so bare with me.

I have a small glass cylinder with silicon lid that seals pretty well,I calculated the volume of the cylinder to be 24 cm^3.
I wanna attach a syringe on the lid in hope to remove air and hopefully air bubbles.
Will it work?
What size of syringe do I need? (in ml)

>> No.11127712

It has been on my mind that a system cannot measure itself. It cannot account for its own thinking. Where can I read more about this? What are the theoretical limits on the ignorance of such a measuring system? This interests me because it means that the measurer is a singularity in its own (scientific) account of the world he lives in. Second, is this concept ever applied to the fields of psychology and sociology? It's well known that people may adjust their behaviour when they are told they should act so-and-so: this is an inherent weakness of the said fields, and I hope this issue has been properly disserted by logicians, philosophers and/or scientists.

>> No.11127733

No. It's not just that the escape velocity is "greater than light speed" (even though this doesn't make sense in relativity), it's that the interior of a black hole is utterly inescapable period. There are no physical trajectories, whether freefall or accelerating, that can escape out of a black hole from inside.

>> No.11127925

I want to double the value 3 six times and sequentially add them together, like 3+6+12+24+48+96. How can I represent this using sigma?

>> No.11127953 [DELETED] 


>> No.11127993

scientifically speaking, why do people who smoke before lectures see the need to sit right fucking next to someone to choke them with their putrid cigarette scent when there are many available seats away from people

>> No.11128030 [DELETED] 
File: 233 KB, 665x665, 20190905_072940.jpg [View same] [iqdb] [saucenao] [google] [report]

Why do people like eat noisily, slurping noodles in the library?
Why do people ask a million inane questions per lecture?
Why do people whip out their laptop in front of you and start browsing bullshit when they should be paying attention?

At least I wash my hands.

>> No.11128034

God I want to be the bunny

>> No.11128046 [DELETED] 

So in our computer lab there is an emergency telephone that's very obviously for...emergencies only.
Last week I was in there doing some work and hear some commotion from an african american student.
"Hello? Yes??" [pause] "There's no paper in the printer." [longer pause] "I said there's no paper in the printer! We need more paper!" Everyone is looking. "Oh...okay." he hung up and left the lab entirely.

>> No.11128056
File: 1.31 MB, 640x360, 124868773.gif [View same] [iqdb] [saucenao] [google] [report]


>> No.11128067

is there an error in this answer? the person wrote 2(a+1) then in the next line wrote 2a+1
shouldn't it be 2a+2?

>> No.11128069 [DELETED] 

*smokes an extra cig just before class, just for you*

>> No.11128162

Ignoring atmospheric effects, if I hold up a plate in such a way that its surface normal points towards the sun, will the solar irradiance on the plate be independent of latitude and time of day?

>> No.11128163 [DELETED] 

Ignoring the atmosphere, yes, it approximately makes no difference.

>> No.11128183

I don't know which exact line you are referring to, but if it is the one I think it is then the value x/2 has to be strictly smaller than 2(a+1), so it can't be 2a+2 and thus they take 2a+1 (and 2a since x/2 should also be equal or greater than 2a)

>> No.11128202

>You need to replace the heating system in your house. The heating contractor is offering you a system that supplies energy at the maximum rate of 40 kW. You know that your house loses energy at the rate of 1.3 kW per degree difference in temperature between inside and outside of the house. The minimum winter temperature in you rarea is−15oC. You want to maintain 20o indoors. Should you go with the heating system recommended by your contractor?

Is this a trick question? 1.3 kW per degree difference in temp means, at worst, we lose 45.5 kW, which is too much for the system being offered to handle (since we want to maintain 20oC inside), right?

>> No.11128208

Thanks anon.

>> No.11128332 [DELETED] 

No, you are correct. You do not want the option he is offering.

>> No.11128371

Hi, /sci/. I'm looking for the most non-brainlet computer science education/regimen I can possibly find. Normally, I'm a /g/ poster, but the average /g/ user shies away from math and all that stuff. Thanks.

>> No.11128442

If you cheat on a test, fail, and the professor posts the grade online, is it safe to assume you didn't get caught?
If you were to get caught, would the professor not have bothered posting the grade?

>> No.11128444

Stop cheating

>> No.11128458

Thanks mate, also regarding questions about gases in thermodynamics, is it fair to assume that they are ideal? For example, I'm given a question about argon and I'm supposed to find something about volume/pressure/etc, is it fair of me to just assume it's an ideal gas so I can use the ideal gas law?

>> No.11128488
File: 97 KB, 413x413, 20190413_062333.jpg [View same] [iqdb] [saucenao] [google] [report]

It depends. Ideal gas law is best at pressures that are small compared to critical pressure and temperatures that are high compared to critical temperature. Otherwise, use a compresibility factor/chart. (Pv=ZRT) You can also use some other equation of state like Van der Waals. There are many options to chose from!

>> No.11128496

ok ty again bby

>> No.11128694

If a polyhedron has 24 vertices and each vertex is connected to 3 edges, how do you calculate how many edges it has?

>> No.11128732
File: 30 KB, 493x260, 110819.jpg [View same] [iqdb] [saucenao] [google] [report]

hi everyone i don't quite understand this problem, my professor didn't talk about this. i don't know what a+bi form means or how to solve this

>> No.11128751

a+bi is complex form, real part is a and bi is imaginary


>> No.11128756

if you take the square root of both sides, you end up with x - 5 = sqrt(-49). i = sqrt(-1), hence -49 = 7i.
x = 5+7i

>> No.11128856

My professor said that lim (a_n)^(1/n) = lim (a_(n+1))/(a_n)) why is this true? What's the reasoning behind it?

>> No.11128878

Like sigma (from k=1 to 6) 3*2^k?

>> No.11129201
File: 112 KB, 768x1024, 1573190182703m.jpg [View same] [iqdb] [saucenao] [google] [report]

Particle physics question.
Suppose an oxygen atom is moving at a constant velocity through space. It passes by another oxygen atom, and immediately binds with it. Does it slow down correspondingly? I'm guessing the answer is yes, but I wanted to ask anyway.

>> No.11129211

What is a_n? And the limit as what tends to what?

You need to clarify the question.

>> No.11129435

why do they mean by, that, during solving, during solving by FEM/FVM people say that solution in particullar "time-step" must "converge"

tl;dr why in FEM solutions must "converge" to some arbitrary values

>> No.11129441

_ denotes subscript and the limit is almost certainly infinity, use common sense

>> No.11129616

if you have 2 blankets and one is warmer than the other, which one should you place on top? or it doesn't matter?

>> No.11129667

For FVM (I don't know FEM), certain simplification are made to the governing equations, this means that the equations being solved aren't actually the correct equations, so the answer we get is an approximate one. This is compensated for by solving the equations multiple times and using the solution of each iteration for the next. If this is done correctly, the solution will converge to the correct value.

>> No.11129721

The information that's missing is that [math] (a_{n})_{n \in \mathbb{N} }[/math] is a sequence of positive numbers, otherwise the n-th root may be undefined when n is even. The full statement is the following:
Let [math] (a_{n})_{n \in \mathbb{N} }[/math] be a sequence of positive real numbers. Then:
[math] \liminf_{n \rightarrow \infty} \frac{a_{n+1}}{a_n} \leq \liminf_{n \rightarrow \infty} \sqrt[n]{a_n} \leq \limsup_{n \rightarrow \infty} \sqrt[n]{a_n} \leq \limsup_{n \rightarrow \infty} \frac{a_{n+1}}{a_n} [/math].
Of course when a sequence is convergent then [math] \liminf = \limsup [/math] and thus you get the equality you were told. I'll explain assuming the limits are both convergent to a real number k

The intuitive reason is simply because [math] \lim \frac{a_{n+1}}{a_n} = k < \infty [/math] basically just tells that the further you go into the sequence, the closer each element becomes to just the previous element times k, or in other words [math] a_{n+1} \approx ka_n [/math]. Apply that for every element to the previous one, and you find that (very roughly), [math] a_{n} \approx k^{n-1}a_1 [/math]. Of course, this estimate could be very inaccurate for small n, but limits don't care about small n. So even if the first term of the sequence may be annoying at first, the bigger n becomes the more irrelevant that first element becomes, since the whole product just behaves like the natural powers of k. And you may already notice what happens if you take the n-th root, in that case.

For the formal proof, you might want to take advantage of [math] \frac{a_n}{a_{n-1}} \frac{a_{n-1}}{a_{n-2}} ... \frac{a_{m+1}}{a_m} = \frac{a_{n}}{a_m} [/math], for n>m, and also the definition of a limit. It's just working with some inequalities but it should be manageable.

>> No.11129722

The equivalent thermal resistance is the same either way so it probably doesn't matter. I'm not entirely sure though.

>> No.11130101

I set A' is a complement to set A, does an element from set A' complement an element from set A.

>> No.11130112


>> No.11130123

What does it mean for an element to complement another element? What does it mean for a thing to complement another thing?

>> No.11130157

it doesn't mean anything. the answer is "no", because the question doesn't make sense.

>> No.11130167

Couldn't you have said that to begin with?

>> No.11130200


>> No.11130527

"the process of digestion normally takes between 24 and 72 hours"

Can stool already in the bowels be influenced by digestion happening elsewhere in the body?
I shat green a mere fourteen hours after eating kale. Trying to figure out if my digestion cycle is abnormally fast.

>> No.11130647

I think the warmer blanket below is better, since the area with a warmer temperature will be concentrated in a smaller volume that way.

>> No.11131000

I'll be re-enrolling as a math major for winter term after a little over two years away from school. The minor is CS, and my first class load will be vector calc, a second programming class (I took the intro already), and physics w/ calc. How would you structure your study plan knowing this? I'm thinking I'll just grind maths, I'm working through Spivak's Calc right now for a refresher, it's obviously way more rigorous than Stewart's calc which is what the class uses, so I think solely studying that will be good enough prep.

On a related note, how many things can you effectively study in parellel?

>> No.11131010
File: 42 KB, 420x279, DarkMatter.gif [View same] [iqdb] [saucenao] [google] [report]

This is a dumb question, but I'll try to explain my logic
Pic related looks like a logarithm.
Logarithms are similar to the arccosh(x) function, like so:
Is it fair to assume that the distribution of mass follows an arccosh(x) function, and from there, try to fit the data to it?
The arccosh(x) function is undefined on (-1, 1). Could this undefined region correspond to the radius of the galaxy's supermassive black hole? Does it correspond to the average mass of the galaxy?

>> No.11131230

Are there any good books about understanding human behavior that aren't psychological mumbo gumbo?

>> No.11131254

I got an answer from another anon, but that post is removed. It said n=0 to 5. But yes, you're right with 3 * 2^n.

>> No.11131669
File: 1.20 MB, 1920x1080, __kirisame_marisa_remilia_scarlet_patchouli_knowledge_komeiji_satori_hijiri_byakuren_and_2_more_touhou_drawn_by_kawayabug__1d4310ba6808d198ae1edc7b60bc1cf0.png [View same] [iqdb] [saucenao] [google] [report]

Ilegible, please try explaining what you want again.
Any smooth closed curve comes with a built-in local diffeomorphism onto the unit circle, by definition.
If the curve doesn't come with a parametrization, you'll need to work over context. If it's star shaped you can use the center point and polar coordinates to find an appropriate parametrization.

At least that's what I think you were asking.
>he doesn't know about fixed point trickery
Assume your house is 20 degrees. It loses at least 1.3*35kW, so 45,5kW. Heating system supplies a max of 40kW, so your house loses heat at 20 degrees, and would lose even more at higher temperatures.
I've got the impression that some lad answered this and it was deleted. Probably zootopiafag.
24 vertices times 3 edges gives 72, since an edge connects two vertices we half that, so 36.
>how do you structure your study plan knowing this
Ask your senpais what subjects are harder or what professors are more rigorous and study for those more.
Alternatively, just study hard.
>Is it fair to assume that the distribution of mass follows an arccosh(x) function, and from there, try to fit the data to it?
Lad, there is an extensive theory out there about linear regression, carefully expounded in statistics and econometrics books.
>Could this undefined region correspond to the radius of the galaxy's supermassive black hole?
No, you'll need much better theory to argue for something like that.
>human behavior that aren't psychological mumbo jumbo
There's economics and game theory. In particular, behavioral economics.

>> No.11131677

Oh, right.
There's the Riemann mapping theorem. I think there was a constructive proof in Bishop's constructive analysis, but it's probably by iteration.
By the by, the radius thing doesn't work for that.

>> No.11132095

So when lights are on, photons bounce around and that's how I see colors and stuff. When I turn off the lights, the bulb no longer emits photons, but how do objects absorb all photons so fast? Is it always guaranteed that there will be objects that absorb all visible EM wavelengths?

>> No.11132624

Light travels at 300 m/μs, so unless you're in a huge room it's going to bounce off multiple surfaces every microsecond. And if that isn't enough to absorb it all, it will travel through 300 km of air per millisecond, which will absorb a lot (notice how much dimmer the sun is when it's near the horizon compared to overhead).

IOW, the only way it's going to keep bouncing around for an extended period without being absorbed is if it's inside a large container with perfectly reflective surfaces and no atmosphere (vacuum).

>> No.11132976
File: 8 KB, 814x262, IMG_20191110_121327.png [View same] [iqdb] [saucenao] [google] [report]

For a motor pump, what would "the electric power consumed" mean? The power before it enters the pump? The power after it goes through the motor pump?
It's for a fluid mechanics problem. Pic related.

>> No.11133059

You know when you're learning physics you start off with all this specific stuff that only applies in particular situations and then you move on to some more general techniques that still seem kind of unrelated and then finally you do classical mechanics properly and it brings it all together? Is there a something analogous to that final step that makes it all work for statistics?

I know a lot of statistics and there are vague strands relating it all together but on the whole it's kind of a big mess.

>> No.11133317

Why does wind form?

>> No.11133345

Not a meteorologist but on a small scale differential heating of the air (ie as the land heats up during the day vs the relatively stable temperatures over water) will give you a difference in pressure and air will flow from high to low. Where I live in summer we get a reliable cool wind off the ocean on a hot afternoon because of this. Large scale patterns are probably the same effect + the earth's rotation (+ tidal forces maybe?) + some degree of self-organising.

>> No.11133571
File: 245 KB, 960x1540, 1569967590800.jpg [View same] [iqdb] [saucenao] [google] [report]

What would be the most efficient way to go about starting to study biology?
It caught my interest and I was wondering where I should start, I understand studying biology implies prerequisites in chemistry, physics and math so I was wondering what order/what resources I should look into.

>> No.11133622

>googling for 30 minutes looking for an answer
>don't understand shit about what people are saying
>open another quora link
>perfect short answer that explains everything I wanted to know
>it's written by a fucking "Middle School Student who does more math than he should"

>> No.11133684
File: 3.09 MB, 4000x3000, IMG_20191110_180020.jpg [View same] [iqdb] [saucenao] [google] [report]

What now besides taking log n before sums

>> No.11133693

Just reuse the trick that went into the first one, that is, multiply by n^2 to remove both sums.

>> No.11133724

but the second sum starts at i, not 1

>> No.11133756

>just study hard
I'm trying but I'm looking to increase efficiency based off my very specific goal. Intuitively, I feel that blasting through Spivak's Calculus is my best bet, since it will turn my brain into a muscular monstrosity, but I also see why this is dumb because it is unrelated to any of the courses I'm taking. So I think I'm going to just go hard on Spivak for the brain gains, and balance that out with some review type sessions for the other material for the domain specific knowledge every now and then.

>> No.11133843

Oh, didn't see that one.
[math]\Sigma_{i=1}^n \Sigma_{j=i} \log n= \Sigma_{i=1}^n (n-i) \log n = \log n \Sigma_{i=1}^n (n-i)[/math]
Evaluating the last sum is left as an exercise to the reader.
Tip: split it into the sum of two sums, i.e. [math]\Sigma (a+b) = \Sigma a + \Sigma b[/math]
>it will turn my brain into a muscular monstrosity
>I'm going to just go hard on Spivak for the brain gains
It really doesn't work like that. You either seriously overestimate Spivak or you're genuinely stupid enough for the brain gains to actually happen.

>> No.11133845

when is the best time to exercise for the benefit of learning? immediately before studying? immediately after? or just any time during the day?

>> No.11133852

do you know what hyperbole is? compared to Stewart's Calculus, it will certainly get my brain better at problem solving and the abstract reasoning that math demands. I've already read half of it, and it definately made me much better at maths, and focusing / thinking abstractly in general. I mean I can't say it's the sole source, but I feel like it was the single largest contributor with Valenza's abstract algebra book a close second.

>> No.11133879

ah shit thanks, havent done math in a long time

>> No.11133892

Twice the sum is:
= n(n+1)
So the sum is n(n+1)/2.

More generally, for any arithmetic sequence (a sequence where the gap between adjacent elements is constant) the sum is the total number of elements times their average: n*(lo+hi)/2. The average of the first and last elements is equal to the average of the second and last-but-one elements and the third and last-but-two and so on. Thus you can replace every element with the average without changing the sum.

>> No.11133913

>most efficient
just start right now and review/learn prereqs only as needed, as they come up. strictly on an as needed basis.

>> No.11134088

is it better to go to a shitty local, state uni where i get free rent and a freelance, fun, low weekly hour job from home or is it better to go to a somewhat decent state uni, pay rent, and probably not have the cushy job anymore?

>> No.11134115

freelance was the wrong word, it's more like work whenever i want, but a certain amount of routine work must be done every week (which takes about 20 hours to do). it's the ideal job as a student due to this and it being doable from home, imo. so I know my studies will suffer if i move and have to work to pay rent in conjunction with studying. but the school is way better; the local uni is like a community college, the other one is probably the best school in the state for my major.

>> No.11134271

Take color coded notes in class, make them pretty so you can admire them, dream of them, and feel proud.
Before the exam, skim over all your notes, condense them into a 1-page "cheat sheet," then remember as much of it as you can. Don't bother with practice problems, that's what homework's for.
Takes like, a couple hours a month, tops, and you will destroy the exams.

>> No.11134474

other anon, just try anki
im not super smart and spend hours weekly on vidya, despite all of that im on 3rd semester at uot that's around top 800 in europe (i know its not prestigous but still) with all subjects passed so far, meanwhile half of my year already dropped out, even passed physics on first try despite it starting at intermediate level and me not ever learning it before
just run it everyday, add new shit that you've had that day on uni, repeat what you have to and you're golden

>> No.11134610

Is there any game that you can play to increase your logic / critical thinking?
I'm solving IMO problems in my free time but I think I might as well try to play some games because they are more fun. I heard things like FTL or StarCraft helps. Is that true?

>> No.11134699

does this mean, a such as b?

>> No.11134731



>> No.11134738

Keep solving IMO problems. If you want to increase your logic / critical thinking for competitions, nothing will help you prepare better than solving actual problems.
By playing games you will only become better at playing those games. Improvements in other areas will be pretty much negligible.

>> No.11134743

The question is describe the numbers not(in italics) in interval [-3,3]

The answer according to the textbook is both |x| ≤ 3 and -3 ≤ x ≤ 3. Isn't this wrong? Wouldn't this describe the number in the interval [-3,3] instead?

>> No.11134746

You are right. The textbook is wrong.

>> No.11134750

Great. Hopefully the author just didn't give a shit about proof-reading the basic review and the actual meat of the text will be reliable. I like how this text is written and the breath of the problems even in the opening chapter otherwise.

>> No.11134851

a|b and a|c a|(x · b + y · c)

>> No.11134861

Someone pls help with this problem:

[eqn]C(p) = \int \limits_{0}^{p} \cos{\big( \frac{\pi t^2}{2} \big)} dt[/eqn]
[eqn]S(p) = \int \limits_{0}^{p} \sin{\big( \frac{\pi t^2}{2} \big)} dt[/eqn]
prove using maclauring series and integration that:
[eqn]C(p) + jS(p) = \displaystyle \sum_{n=0}^{\infty} \frac{(j\pi/2)^np^{2n+1}}{n!(2n + 1)}[/eqn]

>> No.11134862


yes. a | b means a is a factor of b, and likewise if a | c, a is a factor of c. so a is also a factor of (x*b + y*c)

>> No.11134872
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This really looks like the kind of problem where you just swap sin and cos for the power expansions, use the ole rule for integration of power series, and evaluate by hand like a retard, did you try doing that?
Seems like the book is wrong to me.

>> No.11134873


>> No.11134884 [DELETED] 

>This really looks like the kind of problem where you just swap sin and cos for the power expansions

if you apply euler's formula i think c(p) + jS(p) is just the integral of e^(j * pi*t^2 / 2))

>> No.11134923

Ye, but there's a difference between answering and spoonfeeding. I'm perfectly content giving an absolutely horrendous answer and leaving anon to use his own insight to better it.

>> No.11134927

>Just swap sin and cos for power series...
Im dealing with a definite integral tho, how does that look like in the resulting series expansion?

Dont think ill have to deal with an error function

>> No.11134939


well i'm not. i need the practice.

from the integral e^(i...), you use the series definition of e to get the integral over the series whose terms are (pi/2)^k *t^(2k)/k!. taking the anti-derivative of each term, you get (pi/2)^k t^(2k+1)/(k!*(2k+1)), i think.

>> No.11134943

>(pi/2)^k *t^(2k)/k!

(j*pi/2)^k *t^(2k)/k!

forgot the j

>> No.11134967
File: 338 KB, 2340x3072, New Doc 2019-11-10 20.06.04_1.jpg [View same] [iqdb] [saucenao] [google] [report]

My apologies anons, the problem was rather trivial and I just got scared due to how ugly it looked.
Your insight helped me solve it, thank you very much.

>> No.11134968
File: 277 KB, 800x1131, __kitashirakawa_chiyuri_touhou_and_1_more_drawn_by_blackcat_pixiv__90bdf81df6fb8b2ca7eee515b0cf12ce.jpg [View same] [iqdb] [saucenao] [google] [report]

Evaluate the indefinite integral (remember the integral of polynomials? Infinite series do the exact same thing, but the sum is infinite), and do the ole F(b)-F(a).
The F(b) is "probably" in the n=0 component.
Sounds about right.

>> No.11134974

>the F(b)
The F(a).
Is that spanish?

>> No.11134978

Post above you is the solved problem my dude. Thanks anyways bro.

>Is that spanish?
Yes (unfortunately)

>> No.11135091
File: 9 KB, 309x191, Screenshot_2019-11-11-02-50-00-234_com.google.android.apps.docs.jpg [View same] [iqdb] [saucenao] [google] [report]

Does anyone know how to use matlab?
I'm supposed to make a matrix that looks like this, using the loop 'for' function.
If anyone could help, i'd really appreciate it.
I'm a chemistry major, i'm not built for computers

>> No.11135101

No idea how to use matlab, but can't you just define a matrix with [math]a_ij=i*j[/math] for [math] j \leq i[/math] and 0 otherwise?

>> No.11135113 [DELETED] 


k = 1
for j from 1 to cols
for i from j to rows
mat[i,j] = k
k += 1

not matlab syntax but i think that's what you're looking for.

>> No.11135118 [DELETED] 


disregard this. you can still use the loops to access the elements on and below that diagonal, from top to bottom, left to right, but you'll still have to figure out the value of Aij

>> No.11135120


for j from 1 to cols
for i from j to rows
mat[i,j] = j * i

not matlab syntax but you can translate it.

>> No.11135154

For i=1:size(a)(2)
For j = 1:i
a(j) = i*j

Of the top of my head, should work nontheless

>> No.11135296

Suppose that G is a k-regular graph on 2n vertices. Let G1 be the graph G after attaching a vertex x connected to the first n vertices, and let G2 be the graph G after attaching a vertex x connected to the last n vertices. I need to show that the adjacency matrix of G1 and G2 are similar, is there a good starting point for this?

>> No.11135354

Basically how to make multivariate linear regression with random variables without having observations available, just having their expected values and variances. The algorithm should minimize the SE

>> No.11135475

Thank all of you guys!

>> No.11135732

Any anons with integration bee experience here? I was wondering if either of the two integration technique books in the wiki (Irresistible Integrals by Boros or Interesting Integrals by Nahin) are good primer books for a contest like this. And if so, which one? I'm just looking for the most barebones one at the moment since the contest is within a month and I'm just a freshman fag that wants to be able to do at least one of the integrals.

>> No.11135735

Anything specific I should look for? When it comes to epistemology I'm more aligned with the analytic tradition but you have captured ny attention.

>> No.11135738

Is a closed energy loop (100% efficiency) possible?

>> No.11135760

To be more exact, I think this issue can be approached from a more modern perspective with system- or information-theory. Actual mathematical theories outlining the limits of Turing machines or something like that (it's not my area of expertise but you get the idea). Does that exist?

>> No.11135844

I was going to make a new thread, but I will just ask here.
How do I handle a friend who has adopted the EU theory? Whenever the topic of cosmology is brought up, he looks at me like I am a retard who is a sheep that has been brainwashed by the standard scientific consensus on theories of the universe. He has claimed, gravity can not be proved and Einstein's theory of general relativity is wrong, among other things. I usually try to ask him questions to expose his views, however i have no scientific background

>> No.11135878

What's your friends education/research field?

>> No.11135898

which polynomials can we write with coefficients 1 or -1 (binary polynomials) that have real roots?

>> No.11135911

what’s ftl? sc2 def keeps me quick witted

>> No.11135938

We have -x^3-x^2+x+1 has all real roots. notice a pattern?

>> No.11135978

I'm writing the measures section of a lab report right now. When I refer to the independent variables, do I phrase it as "the first independent variable "measured"...."? It's only a binary variable so I'm just a bit confused as to whether it's correct to use the word "measure".

>> No.11135987


>> No.11136018

im looking for chemical reactions between two liquid substances at stp which are highly endothermic and produce a large amount of highly energetic reactants like molecular hydrogen
in the presence of a catalyst is ok as long as it doesnt erode the shit out of the catalyst
the safer to handle the better
does /sci/ know? thanks in advance

>> No.11136098

I am a computer science student and I am taking a course on quantum mechanics this semester. I hardly understand anything while most of the others (who mostly are CS students as well) seem to understand everything well enough. What are some good sources to learn quantum mechanics for someone without much background in physics like myself?

>> No.11136115

I know nothing about digestion, but Kale is like 80% water content so I’d assume all those green fluids got absorbed quickly and mixed with the poopoo

>> No.11136130

Is this bait?
Practice questions are everything

>> No.11136371

How good are your maths? Are you familiar with linear algebra and/or complex numbers?

>> No.11136454

Yes, I've had linear Algebra in first semester and complex numbers were part of that.

>> No.11136576

Have you also covered orthogonality and eigenvalues? If you know all of this (plus integrals), you should be set for an intro course. But the formalism can be challenging to understand, that's not something computer scientists struggle with. I'm a physics master student and I learned QM through Griffiths, which is a really good book, perhaps more pedagogical Anons know what you need exactly. If you have a specific question I can try to explain it here.

>> No.11136646

It's not something just* computer scientists struggle with. My bad.

>> No.11136676

When I first covered QM we used some chapters in Serway Moses and Moyer that go through it's development historically, starting with like the photoelectric effect experiments and working up to atomic orbitals. It's not particularly rigorous but if you're having conceptual problems instead of mathematical ones it might give you something to work with.

>> No.11136715

Thank you, I'll look into those.

>> No.11136817
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Anyone know good resources for curve shortening flow?

>> No.11137101
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>> No.11137157


>> No.11137166

He is high school educated and works in IT sales.

>> No.11137170

Faster than light. It's a rogue-like strategy / resource management game. You can pause but it's a bit intensive near the end.

>> No.11137196
File: 33 KB, 400x524, 09.jpg [View same] [iqdb] [saucenao] [google] [report]

dont leave me out to dry like this bros

>> No.11137268

it's faradays law, find the magnetic flux, differentiate, multiply time number of turns of coil (300) and evaluate at 2.
if you don't know how to find the magnetic flux then you're probably kinda fucked, permeability*n (of solenoid)*I*0.4*area (of solenoid too)

>> No.11137328

If you're not a physicist either then the whole affair is pretty pointless and you should just laugh it off. If he one-ups you once in a while that's ok, you aren't supposed to know everything either, while you can look up experimental verification of general relativity at any point in time and challenge him with that. Either he has a crackpot theory to debunk it or he doesn't have a response at all. If you are an actual physicist it may be worthwhile to look into EU a little bit and lampoon how unscientific it is in detail. It depends on how scathing you want to be, I don't like to insult people but humiliation is sometimes the best way if you really want him to stop believing in conspiracies, there's doubtlessly some psychological research on the topic.

>> No.11137410

How do I calculate the volume percentage of an analyte using GAS CHROMATOGRAPHY?

I've been given the response factor AND the areas of peaks

>> No.11137417

I know how to find it but I was using the wrong area, I shouldve used .15 instead of .4
.15 gives 1V which is the correct answer and I just misread the answer page
fuck me

>> No.11137568

No it's literally how I got through college
>Practice questions are everything!
Yeah, the first time you do them. aka homework.
You solve one, you've solved a million

>> No.11137570

Alright, let me see if I understand.
You have an n-dimensional vector [math]X = (X_1, ~ ..., X_n)[/math], where all the [math]X_i[/math] are independently distributed random variables, and you want to find a vector [math]v_i = \alpha i + \beta[/math], where alpha and beta are real numbers, that minimizes the norm of the vector [math]r_i = X_i - \alpha i - \beta[/math]?
If I had to guess, there's no closed form solution for arbitrary X_n.
Phenomenology of Spirit and Science of Logic, of course. What else?
>limits of Turing machines
Computability theory?

>> No.11137597

It would mean the power that is directed to or consumed by the pump...kinda self explanatory. If it was talking about energy per unit time imparted to the fluid it would be called hydraulic power.

>> No.11137672

please help if anyone knows

>> No.11137722

Have real roots or only have real roots?

>> No.11137779

>What else?
I'm reading through this summary but I'm not sure in what part my question is supposed to be treated. I mean, the basic metaphysical notion of the self-aware subject is certainly present, but I think Hegel branches off to psychological questions (collective consciousness etc.) rather than epistemic details concerning existence and essence (this whole curiosity of mine is partially existentially motivated), and I don't suppose he proved any rigorous, system-theoretic theorems. But if there's anything that may be of use to me I'd be grateful if you referred me to the specific chapter/paragraph.

>Computability theory?
This is what I'm thinking about, and I will look into computability theory. Do the computations in this field also involve information about an aspect of the machine itself? The concept of "measuring a measurement" is obviously infinitely recursive, but measuring external events is not, so where is the line drawn? That's what I have in mind. Thanks for you responses by the way.

>> No.11137807 [DELETED] 


there are lots of polynomials like that. what do you mean by "which"

>> No.11137892

>Probably zootopiafag
really makes me think why jannies have more of a problem with me discussing science and engineering in earnest than the latest racebait/incel general/niggers r dum thread

>> No.11137983

Only real roots.
What is the form of those polynomials?
I've been trying to find a pattern by looking at sign switches (like using Descartes Rule of Signs) but it's not strong enough.

>> No.11138066
File: 39 KB, 242x170, help.png [View same] [iqdb] [saucenao] [google] [report]

Why did the prof write [math]\delta S[/math] instead of [math]dS[/math]? I thought entropy was a state variable? What's the difference between using delta to denote an inexact differential and putting a stroke through the d?
@ about 30 minutes in

>> No.11138074

I didn't even know that [math]\delta S[/math] meant something different from [math]dS[/math].

>> No.11138087

Mathfag here learning QM. I was pretty on board bra ket notation until I started seeing shit like this


Wtf is a ket in the integral? What does [math]\mid x\rangle[/math] even mean?

>> No.11138096

do you know thermodynamics?

>> No.11138105

not that well honestly, I did take a thermo class but the professor was total joke

>> No.11138107

it's just a column vector, anon

>> No.11138113
File: 1.17 MB, 884x1137, __remilia_scarlet_touhou_drawn_by_yuki_popopo__aa7e67619508fef8151d02ba480cf9a6.png [View same] [iqdb] [saucenao] [google] [report]

Oof, that's the really hard case. I've got half the classification down, might finish it and post later. Hopefully I'll find some symmetry which lets me turn it into the other one, or I'll start having to appeal to, dare I say it, Newton's formula.
Not sure what is it you expect from jannies.
Either the codifferential or the delta physicists use for Lagrangians.

>> No.11138122

>Not sure what is it you expect from jannies.
I expect them to care whether or not /sci/ related topics are being discussed.

>> No.11138142

>Either the codifferential
looked that up, this is surely not what he is talking about
>the delta physicists use for Lagrangians
I'm not familiar with that. explain?

>> No.11138172


>> No.11138280
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I found this in my attic; the fuck am I reading?

>> No.11138520


>> No.11138551

Can someone explain to me how the evaluation map of real valued polynomials [math]R[x][/math] has [math]E_{va}(0)=0[/math]? For example, consider [math]f(x)=x^2 + 2 \in R[x][/math]. Then [math]f(0) = 2 [/math]. What am I missing here?

>> No.11138591

How do you study?

Seriously, i have 6 subjects (60 credits) to study each semester and everything is being rushed by my shitty professors. I don't see the point of going to lectures given the fact all the lectures are on my student account - 6 hours are wasted everyday i feel.

How do you attain all that information in 2 and a half months (only 4 weeks now)? Do you take notes? - i try, but notes just feel like wasting time. It takes me hours to condense shit and it feels like i'm just repeating the lecture slides or textbooks.

And then sometimes, i have to learn a concept that just doesn't stick for some reason. Which means i can't go onto the next chapter because you need to know the shit from the previous chapter to move on.


>> No.11138594

>60 credits/semester
no you dont

>> No.11138669
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Can someone help me with this? Not really sure what to do here. For a, I assume the average should be 0 mainly because it's a sinusoidal wave, but I don't know how the k values and probability come in to play.
I also know that the variance is [x^2] - average^2, so I guess just x^2 if the average is 0. Don't really know how to attempt this, though.

>> No.11138951

how is the map defined ?

>> No.11138966

The evaluation map maps polynomials to their respective values for fixed elements of the coefficient ring (so [math] \mathbb{R} [/math] in this case). In fact it not only maps 0 to 0, it is a ring homomorphism, so it meets the other properties too. But when we say it maps 0 to 0, we don't mean it maps the polynomial evaluated at 0 to the value 0, since the evaluation maps receives polynomials as inputs and not elements of the coefficient ring. What we mean then is that the evaluation map maps the 0 of the polynomial ring (so p(x)=0) to the value 0, for any fixed value of x, which is trivially true.

>> No.11139143

Just use cos(a+b)=cos(a)cos(b)-sin(a)sin(b) for a), and plug in manually for b).

>> No.11139152

Any med students or researchers want to tell me why it's been so difficult to cure or at least reduce the impact of cancer?

It just seems strange to me that with all the various groups (nonprofits, governments, businesses, etc) and the billions upon billions of dollars spent as well as just the raw number of bright people working on it that we haven't made much progress in the field.

Anyone who knows more on the topic care to explain it to me? I know I could totally be missing something.

>> No.11139169

Faster Than Light
It's a space sim where you are the crew of a ship

>> No.11139684

If f(x)'s limit at a is 0, is the limit of f(x)g(x) also 0 at a for any function g that is defined in the same set as f?

>> No.11139738

Set [math]f,g : \mathbb{R} - 0 \rightarrow \mathbb{R}[/math] with [math]f(x) = x[/math] and [math]g(x)=1/x[/math].
>what if I require that they're both defined at the entire real line
[math]f(x)=x[/math], [math]g(x)=1/x ~ for ~ x \neq 0, ~ 1 ~ otherwise[/math].
>what if I require g to be bounded and defined on some punctured neighborhood of a
Then yes.
In fact, in that case, we don't need to even require continuity of g, and if we do, the Weierstrass supremum theorem helps pretty often.

>> No.11139761

Thanks for the help!

>> No.11139769

I have a stupid question:

►Why are we still on Earth and not in based Moon?

>> No.11139868
File: 127 KB, 768x474, Screen Shot 2019-11-12 at 9.53.38 AM.png [View same] [iqdb] [saucenao] [google] [report]

I don't understand this answer. The question is when does [math] (x+y)^5 = x^5 + y^5 [/math], and I get it ok up until the line below "Substracting this equation from" in pic related. I know that
[math] (x+y)^5 = (x+y)^2(x+y)^2 [/math], but I don't know why I'm supposed to substract [math] x^3 + y^3 + 2x^2y + 2xy^2 [/math] from it, and I don't really get what proceeds after that. Any tips?

the question is from Spivak's calc, chapter 1, problme 16d

>> No.11139964

He just subtracted zero, anon.

>> No.11139968 [DELETED] 


what if you look at the factored form: c(z-c1)(z-c2)....(c-cn) ?

i think you'd have to have c = +-1 , and each c_i = +-1, so those the roots would also have to be either +- 1.

still in most of those cases, the expanded form has coefficients other than +-1, but i think it would be subset of the polynomials whose roots are +-1.

>> No.11139969

aw man, lol. at least i posted in the right place, thx =)

>> No.11140025

Ok, now I don't understand how [math] (x + y)^3 = xy(x+y)[/math] implies that [math](x + y) = 0 [/math] or [math] xy = 0 [/math] in this case. I have no idea how I would've seen that myself or how to justify it.

>> No.11140104

What's different between carnivores and herbivores in terms of metabolism?

What are the drawbacks of each? Why can't every animal make their own protein from grass?

>> No.11140152

>how this implies that
It doesn't.
The xy=0 is from earlier, and he never said (x+y)=0.

>> No.11140260

towards the bottom of the screenshot it says "So either x + y = 0 or .." I don't know how that jump was made from (x + y)^3 = xy(x + y). Thanks for replying.

>> No.11140272

Ah, right.
Essentially, if it isn't zero we can divide out x+y on both sides, and then we get (x+y)^2=xy

>> No.11140336

I assume that you understand up to the point:
> or x^3+2x^2y+2xy^2+y^3=0
The next step is rearranging that expression, which is "close" to the expansion of (x+y)^3:
=> (x+y)^3-x^2y-xy^2 = x^3+2x^2y+2xy^2+y^3 (subtract x^2y+xy^2 from both sides)
=> x^3+2x^2y+2xy^2+y^3 = (x+y)^3-x^2y-xy^2 (swap LHS and RHS)
=> x^3+2x^2y+2xy^2+y^3 = (x+y)^3-xy(x+y) (isolate a common factor of xy from x^2y+xy^2)
So, the previous assertion:
> x^3+2x^2y+2xy^2+y^3=0
(x+y)^3-xy(x+y) = 0
=> (x+y)^3 = xy(x+y)
This is trivially true if x+y=0 (both sides will be zero), in which case x=-y. Otherwise, x+y is non-zero so we can divide both sides by x+y to get
(x+y)^2 = xy
=> x^2+2xy+y^2 = xy (expand the square)
=> x^2+xy+y^2 = 0 (subtract xy from both sides)
Applying the quadratic formula gives y=x(-1±i√3)/2, i.e. the only real solution is x=y=0. Apparently this has already been dealt with in problem 15.

>> No.11140495

Oh I see (duh!), thank you that's very simple.

Thank you as well. This line in particular is where I was lost:
>This is trivially true if x+y=0 (both sides will be zero), in which case x=-y. Otherwise, x+y is non-zero so we can divide both sides by x+y to get
(x+y)^2 = xy

>> No.11140636

scientifically speaking, what's the best morning routine?

>> No.11140645

>wake up
>immediately look at your phone
>decide to jerk off real quick
>then go to the bathroom, brush teeth, shit, etc.
>skip breakfast
>look at phone and get distracted for a couple more minutes
>leave the house late
>smoke two cigarettes on the way to work/school
haha im just joking haha

>> No.11140661
File: 94 KB, 850x531, __patchouli_knowledge_and_remilia_scarlet_touhou_drawn_by_terimayo__sample-ad96284c916a2e5c6b26afd100f16342.jpg [View same] [iqdb] [saucenao] [google] [report]

>wake up
>turn on light
>make alarm stop
>have two or three coffees in a row in a state of dizziness while checking your email, fiddling with random objects and thinking about stuff
>brush teeth while pissing
>dress up and apply deodorant
>check if you picked up your keys
>leave home

>> No.11140682
File: 166 KB, 334x316, bun4.png [View same] [iqdb] [saucenao] [google] [report]

why is that touhou holding kafka's metamorphosis?

>> No.11141224
File: 39 KB, 804x135, 1Mid1sh.png [View same] [iqdb] [saucenao] [google] [report]

asking on SQT because I probably did a stupid proof.

We know that there exists an N such that if b >N, then |int_1^b g(x)- A| < epsilon for some A. Since g > |f|, we also know that if b > N then |int_1^b f(x) - A| < epsilon.

this feels incorrect, can someone guide me

>> No.11141251
File: 3.22 MB, 2507x3541, __flandre_scarlet_and_remilia_scarlet_touhou_drawn_by_yada_xxxadaman__dec0bcc6afe68c7527007ab4127ebad4.png [View same] [iqdb] [saucenao] [google] [report]

Great eyes.
Like a bunny.
Does R mean something like "locally integrable functions" or "measurable functions"?
Because if it does, you just need to partition R (the real line) by the naturals, split up the integral from one to infinity into the sum of those integrals from one integer to the next, and then bound the infinite series by the similar infinite series associated to g, and show it converges by the trivial argument.
Your argument is nonsense, to be entirely honest.

>> No.11141261

It means Riemann integrable functions

>> No.11141271

You can tell your argument is wrong because the value of the integral of g(x) may be very different from the value of the integral of f(x) and even |f(x)|.

I'd approach it like this: By absolute convergence (which we can prove by cauchy criterion) we instead prove that [math] \int_1^{\infty} |f(x)| dx [/math] exists and converges.

We define [math] F(x) = \int_1^{x} |f(t)| dx [/math]. It is clear that F(x) is monotone (i.e. it is increasing) and it is also bounded by [math] \int_1^{\infty} g(x) dx [/math]. Hence [math] \lim_{x \to \infty} F(x) [/math] exists.

>> No.11141282

There's a theorem in baby Rudin (6.12) that says if f1 < f2 on [a,b], then int_a^b f1 dx <= int_a^b f2dx

Why wouldn't it apply here (since for any b, f < g on [1, b] so the integral is also less)?

>> No.11141290

It is less but when you say
>|int_1^b f(x) - A| < epsilon.
notice that you are implying that the integral will converge to A. But that can't be because if a certain g(x) works, then so does g(x) +1, and g(x) + 2. Can't have 3 different limits, johnny boy.

>> No.11141294

Fuck, I forgot about muh deviations within the partition.
You can correct it by considering that g needs to decrease really fast, tho.
Also works, but depends on the theorems you have on hand.
Because no.

>> No.11141307

I fucked this one up. If a certain g(x) works, so does 2g(x) and 3g(x) and so on. Not g(x) +1 because improper, small brain.

>> No.11141309


sorry I think I'm just slow in the head, I'm not trying to challenge you or anything I think my proof is also wrong but I'm just having a hard time understanding where I went wrong,

since the int_1^b f(x) < int_1^b g(x), and

since |int_1^b g(x) - A| < epsilon, then int_1^b g(x) < epsilon + A

so int_1^b f(x) < epsilon + A,

but I guess the reason why this proof doesn't work is because we don't know that -epsilon + A < int_1^b f(x) so we can't conclude anything.

I hate analysis so much, I think I just want to stick to smaller brain math like combinatorics

>> No.11141315

The mistake is in the third line. In particular, you can swap the inequality around since the integral is always smaller than A.

>> No.11141323

>swap the inequality around
My bad, I'm slowly going insane.

>> No.11141347

This is just the Comparison Test for improper integrals, right?

>> No.11141352 [DELETED] 
File: 95 KB, 923x924, 71267238_469926987064280_715848843643154787_n.jpg [View same] [iqdb] [saucenao] [google] [report]

Does anyone have a __They Live__ shop of this picture?

>> No.11141354

I remember you starting that thread a couple days ago. Fuck off.

>> No.11141368

Given that they only finished the mural yesterday, I doubt that.

>> No.11141376

Nah, I'm not mistaken. It was some gay bullshit like
>hey /sci/, is there any way we can fuck this up?
with a picture of the unfinished mural

>> No.11141419

I saw the unfinished mural and though that it had a very fascist aesthetic, so I decided to ask here. It is more /pol/, but it is tangentially related to /sci/, and I thought maybe someone here would deliver.

>> No.11141571

When I put 2 into prime factor calculators it gives me the answer of either "2" or "2*1". What's up with that? Surely both answers are wrong.

>> No.11141588

i mean 2*1 is technically wrong since 1 isn't a prime and if it were considered as one then the prime decomposition of any number would not be unique, unless for whatever reason their * stands for ^ and they mean 2^1 which i guess would be a more complete answer
but what problem do you see with just 2? what answer were you expecting to begin with?

>> No.11141604

>fascist aesthetic
Sounds right up your alley then. Go back to your containment board, fag.

>> No.11141825

Not really. Her fundamental thesis is that we shouldn't involve and engage the stakeholders in society who currently propagate our fossil fuel economy; that coming to a compromise between equals for how to move on from our current situation is "childish". Her message is one of fascist and authoritarian action. Maybe you are confused about who is the Nazi?

>> No.11141837

>Her message is one of fascist and authoritarian action
Sounds right up your alley then. Go back to your containment board, fag.

>> No.11141891

You keep using that word. I don't think it means what you think it means.

>> No.11141901
File: 24 KB, 400x382, 1500361938377.jpg [View same] [iqdb] [saucenao] [google] [report]

You see this? It means "NOT WELCOME." Back to your shithole.

>> No.11142078

I can program, but struggle finding motivation to do so. I have fun doing Project Euler type problems and I’ve been leafing though this competitive programming book: https://cses.fi/book/book.pdf, but this stuff feels superfluous.

I guess what I’m getting at is that I want to program recreationally but don’t quite know how to do so in a manner I enjoy. Any “real project” is either unwieldy in its tedium or its already been done before, and better.

I downloaded Turtle Geometry and The Algorithmic Beauty of Plants in hopes of that interest taking off. Maybe I’d enjoy making a little game using finite automata and L-systems, or something. Any ideas would be appreciated.

>> No.11142098

So in relation to the above, in case it wasn’t clear: any fun /sci/ or /mg/ approved programming ideas would be cool.

>> No.11142113

I'm really bad at coming up with small projects that feel worthwhile but if you want a problem set the Rosalind bioinformatics ones are pretty good.

>> No.11142285

>what answer were you expecting to begin with?

Good point, I retract my question

>> No.11142326

Would you refer to the set 4,9,25,49,121 etc as prime squares? The numbers themselves aren't prime but they are prime numbers squared. Not sure what to call them

>> No.11142336

I would call them squared primes

>> No.11142518

squares of primes

>> No.11142643


>> No.11142711

how do you prove that [math]\frac{dt}{dt'}=1-\hat{n}\cdot\vec{\beta}[/math]? what does it even mean?

>> No.11142792

Cellulose is really hard to digest, so herbivores have strategies including multiple stomachs, chewing the cud (regurgitating partially digested food, chewing it, then swallowing it again), and/or coprophagy (eating faeces of partially-digested food).

This leaves a niche for predators to feed on all that ready-processed food walking around. But obviously you can't have an ecosystem with nothing but predators; something has to be at the bottom of the food chain.

You could theoretically have an ecosystem with nothing but herbivores. But they won't live forever, so something may as well put the carrion to use. And from there, there's no particular need to wait for the herbivores to die naturally before eating them.

>> No.11143205 [DELETED] 
File: 4 KB, 343x182, mpfrtrfrpfprtrfrsmalamasamampfrtffffffffsniffitgoddamnsniffitdmspspsdsds.png [View same] [iqdb] [saucenao] [google] [report]

assume this is a slingshot, so you're pulling at the top of the triangle. g = 6cm, so we've got that s = sqrt(h^2+9).

i want to find an expression for ds/dt in terms of dh/dt and h. I use ds/dt = ds/dh * dh/dt and end up with ds/dt = h/(sqrt(h^2+9)) * dh/dt. i'm given that h rises with a speed of 2 cm/min. now, assuming that the height has reached 11 cm, i find that s is growing by 1.93 cm. does that sound right? sounds like a lot to me desu.

>> No.11143246

Ok boys, new question: at what temperature (high, low is easy google) are nerves permanently damaged? If using heat as a method of torture, what would be the maximum temperature used before nerve damage lessened the sense of pain.

>> No.11143331

sounds right to me

>> No.11143349

Looks like nonesense, but I could be wrong.

>> No.11143478

I'm guessing this is proper time?

>> No.11143480

Does L'Hospital's rule apply in complex analysis? Like can you show that [math]\lim\limits_{z\to0}\frac{\sin z}{z}=1[/math] by L'Hospital's? I know the preferred way is by using power series, but I was just curious if L'Hospital's still applies.

>> No.11143491

>small brain
>apologizing unnecessarily for not conveying information properly on a nazi-pedophile-weeb forum
You all need to stop doing this. We already know you're stupid, announcing this only makes you a target for midwits to attempt opportunistic cruelty towards you

>> No.11143541

What stats courses should I take for physics? Read, "should," I get that stats isn't usually required for physics majors for a reason, but I want to know what stats knowledge you guys have found useful since I have space for quite a few electives

>> No.11143595

What are the benefits of blood donations (I'm counting here normal donation, plasma and platelet donation)? My family keeps asking retarded questions on why I donate when I could simply not, but the only thing I've noticed is that I have lower blood pressure for some time after.

>> No.11143639

In some countries after 10 blood donations you are exempt from paying for certain medical services.
Other benefit is that you will help someone who is in dire need for blood transfusion.

>> No.11143645

read a book on probability and measure instead of wasting months of your life in a stats class filled with brainlets. you can and should self teach probability theory, its very useful for stat mech and qm

>> No.11143659

I would argue there is no true altruism here. Everyone is doing it for some selfish reason - making yourself feel better knowing you helped someone, payment, other bodily benefits among other things. We don't have any exemptions like you mentioned, but I did read that if we need some service like a transplant, previous donors have priority. But still, I was hoping for more immediate personal benefits - I did read that blood donors have lower levels of cholesterol and live longer on average, but causality is not clear on this one

>> No.11143713

>Particle physics question
this is not a particle physics question
> Suppose an oxygen atom is moving at a constant velocity through space. It passes by another oxygen atom, and immediately binds with it. Does it slow down correspondingly?
If the other atom is at rest, then by conservation of momentum the combined atom will slow down. Is that what you ask?

>> No.11143732 [DELETED] 


how did this nigga go from 8/10 to 8/5... bruh da fuck.....

>> No.11143785
File: 5 KB, 232x119, fads.png [View same] [iqdb] [saucenao] [google] [report]

why doesn't [[ebx]] work and i have to do it this way around?
(i need to decrement the value that's under the address stored in memory to which i have address)

>> No.11143808

I think you could do
sub [eax], 1
instead of
mov ebx, [eax]
sub ebx, 1
mov [eax]. ebx

[[ebx]] doesn't work because there is no processor opcode that does a double dereference like that.

>> No.11143879

ah thanks, the more i do in assembler the more annoying it gets

>> No.11144268

I see, I should've figured anyways since most of the stats I've used so far has been error propagation, and obviously I learned it from Taylor's book. Thanks anon

>> No.11144287

Is it correct to say that a projective module is a module P such that every morphism onto it from any module has an inverse on the right that is also a morphism?

I'm trying to understand what a projective module is and why it's useful or important. I know the "lifting" definition but I don't get what it's trying to say, and I'm trying to work with its characterizations instead. For example I've seen projective modules be referred to as locally free modules, but I also don't get what's that's supposed mean since having a basis locally doesn't really seem to make too much sense, and I haven't seen someone define that property instead of just mention it (any textbook I should read that has that definition, by the way?). I've also seen the short split sequence "definition" (which we learned as a theorem), that states that a module P is projective iff every short exact sequence [math] 0 \longrightarrow A \longrightarrow B \longrightarrow P \longrightarrow 0 [/math] is split. Now, among all the characterizations of short split sequences, I remember that a short sequence is split iff the morphism from B to P has an inverse morphism to the right, and since that's supposed to happen for any module B, that's where I get my "definition" in the first paragraph, where I try to drop the context of short exact sequences and just mention surjective morphisms in general. Is this idea good enough, then? Also anyone has a better way to understand the idea of projective modules?

>> No.11144355

Just write a preprocessor that translates your N-indirection into the appropriate instructions and then run it through the assembler.

>> No.11144485

Yeah, just power expand the numerator and the denominator around the point you want to evaluate (in other words, you pretend the point is 0) and cancel out x^n s. The remainder of nonconstant terms vanish.

>> No.11144503

wtf is this https://www.symbolab.com/solver/integral-calculator/%5Cint%20sqrt%5Cleft(x%5E%7B3%7D%2B1%5Cright)dx

>> No.11144893
File: 35 KB, 738x550, SumatraPDF_2019-11-13_23-56-50.png [View same] [iqdb] [saucenao] [google] [report]

can somebody solve it step-by-step?

>> No.11145003
File: 46 KB, 738x550, 1573707505797.png [View same] [iqdb] [saucenao] [google] [report]

complete the drawing so you have more friendly shapes like triangles and quadrilaterals instead of that weird thing
work out the angles from the bottom and the top to the middle quadrilateral, using stuff like supplementary angles and the such
and i think you can finish it finding with the middle quadrilateral

>> No.11145022

that's what you get when you try and find the antiderivative of an arbitrary function.

>> No.11145316

I'd like some help with one of my practice paper.
Consider functions from a set with 5 elements to a set with 3 elements. How many of them are surjective?
My logic is as follows:
Since we want to partition the domain into 3, there are (7C2) ways of doing so. this multiplied by the number of ways for it to be matched with the codomain 3! Thus my answer is (7C2) * 3! = 126, which is different from the correct answer (150). Can someone point out my error?

>> No.11145317
File: 1021 KB, 500x374, 1565952029924.gif [View same] [iqdb] [saucenao] [google] [report]

What's the tern that describes the condition where one point continuously approaches another stationary point for infinity? Such as in the case of repeatedly halving a number forever with respect to zero.

>> No.11145332
File: 43 KB, 1029x100, lZfIhJU.png [View same] [iqdb] [saucenao] [google] [report]

anyone know how to go about this?

>> No.11145335
File: 69 KB, 480x1349, FF23.jpg [View same] [iqdb] [saucenao] [google] [report]

This problem has me thinking about the general case where 60 is a function of θ which I have labelled as y. I feel like there is some three dimensional solution to this. Maybe if the red/blue line was a flag pole or something, purple being a shadow from some source.

>> No.11145403
File: 13 KB, 485x411, why.png [View same] [iqdb] [saucenao] [google] [report]

Why are these two functions the same?

>> No.11145420

Anon I...

>> No.11145442

I'm sorry.

>> No.11145447

what's the value of floor(x) between x=n and x=n+1?

>> No.11145461


>> No.11145472

Alright, I have a silly question. What's the most energy-efficient way to turn elemental lead into not lead? Doesn't have to be gold, per se, but ideally anything else that isn't so toxic to humans?

>> No.11145510
File: 19 KB, 644x154, Capture.png [View same] [iqdb] [saucenao] [google] [report]


Been doing numerous integration by susbtitution questions and whilst I am getting to grips with it, I am not sure how to do the latter question. Are you supposed to let u = e^t^3 then differentiate and rearrange for t? I am not sure if the ^3 cancels the e so it'd be just t or any other way of differentiating it.

>> No.11145513

Several pharmaceutical companies have developed and market specific inhibitors or therapeutic monoclonal antibodies to inhibit the activity of a ReceptX transmembrane receptor. This receptor has tyrosine kinase activity.
In their MA, the indications for these drugs specify that they can only be prescribed for lung cancer when the tumour overexpresses this receptor.
No company currently offers the pulmo-Test, an in vitro diagnostic test capable of detecting overexpression of the ReceptX receptor, in lung cancer. Your R&D team wishes to develop a strategy to occupy this market sector of the Medical Diagnostics industry.
Make different (motivated) proposals to your management, detailing the stages of development (design), validation, (performance verification) of your tool. The commercial approach (marketing for whom? in what form? ease of use etc...) must be specified.
Someone has some ideas?

>> No.11145549

sub t^3, look at the numeric value given in the answer and the limits of integration

>> No.11145602
File: 1.47 MB, 1906x2149, Comfy.gif [View same] [iqdb] [saucenao] [google] [report]

I got the answer, thank-you very much!~

>> No.11146195


The Earth really is flat, isn't it? Oh fuck.

>> No.11146254

thanks, and also bumping my original question

>> No.11146319

Rather than retyping my problem, I'm going to post an exact replica I found on physics forums (the poster descrubes my exact thought process and exactly where I'm stuck):

Like a huge faggot, he left the thread by saying he figured it out, basically, and did not fill in future readers. But in particular I am confused by the line he mentions:

>then our formula isn't actually [math]b2−4c<0[/math] but [math]b2/a−4c/a<0[/math]

>> No.11146326
File: 65 KB, 1050x1050, Zeno_Achilles_Paradox[1].png [View same] [iqdb] [saucenao] [google] [report]

Not sure what term you're looking for, but you're probably thinking of Achilles and the tortoise paradox

>> No.11146365

what's the healthiest way to use nicotine? i definately notice the brain gains when I'm on it

>> No.11146413
File: 137 KB, 1003x323, Screen Shot 2019-11-14 at 10.19.31 AM.png [View same] [iqdb] [saucenao] [google] [report]

Pic related is the problem. I just do NOT understand how the first term is squared. I can only arrive at the same solution but with only the numerator squared, not the denominator.

It's just a complete the square problem, so I get:
[math] \frac{b^2}{a} - \frac{4c}/{a} [/math], I don't know how I'm supposed to get (b/a)^2.

>> No.11146465

ok, i think i get it, but I'm not sure why the author would do it this way. why hault the algebra at
[math]a(x+\frac{b}{2a})^2 + \frac{c}{a} - \frac{b^2}{4a^2} < 0 [/math]?

from here I can see how to get [math](\frac{b}{a})^2 - \frac{4c}{a} < 0[/math], but like why not distribute the [math]a[/math] first in the above to get [math]a(x+\frac{b}{2a})^2 + c - \frac{b^2}{4a} [/math], and then get the inequality [math] \frac{b^2}{a} - \frac{4c} < 0/math]?

>> No.11146478

fuck, sorry bout the tex:
>and then get the inequality [math] \frac{b^2}{a} - \frac{4c} < 0[/math]?

also, this:
was supposed to be

>> No.11147161


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