/sqt/ /qtddtot/ - stupid questions thread

[Anonymous No.12618121]

RIP anime bro edition

Formerly >>12592403

>what is /sqt/ for?
Questions regarding math and science, plus related advice requests.
>where do I go for other questions and (advice) requests?
>>>/wsr/ >>>/g/sqt >>>/diy/sqt >>>/adv/ etc.
>how do I post math symbols (Latex)?
https://imgur.com/MDiglsS.png
>a plain google search didn't return anything, is there anything else I should try before asking the question here?
https://scholar.google.com/
>where can I look up if the question has already been asked here?
>>/sci/
https://boards.fireden.net/sci/
>how do I optimize an image losslessly?
https://trimage.org/
https://pnggauntlet.com/

>where can I get:
>books?
https://spoon.wiki/Books
https://stitz-zeager.com/
>articles?
sci-hub.st
>book recs?
https://sites.google.com/site/scienceandmathguide/
https://4chan-science.fandom.com/wiki//sci/_Wiki
http://math.ucr.edu/home/baez/physics/Administrivia/booklist.html
>carreer advice?
https://sciencecareergeneral.neocities.org/
>help with calculus?
https://spoon.wiki/WolframAlpha
>charts?
https://imgur.com/a/JY6NNeL
https://imgur.com/a/0qDEgYt
>tables, properties and material selection?
https://www.engineeringtoolbox.com/
http://www.matweb.com/

General advice for asking questions here:
>attach an image (animal images are best. Grab them from >>>/an/)
>avoid replying to yourself
>ask anonymously
>remember to check the Latex with the Tex button on the posting box
>if someone replies to your question with a shitpost, ignore it
>avoid arguing with Yukarifag
>do not tell us you came from whatever the fuck board, /pol/ in particular
>do not mention how [other place] didn't answer your question so you're reposting it here
>If you use j for the complex unit, put a ¿ somewhere in your post or use emoticons I will automatically ignore your question. I don't actually know about everyone else, but you shouldn't assume they're too far off about whatever random things they dislike

[Anonymous No.12618227]

Asking again since no one replied in the previous thread, this time with an image from /an/
Does [math] x \mapsto f(x) [/math] mean exactly the same thing in mathematics as [math] \lambda x. f(x) [/math] does in computer science (specifically lambda calculus)?

[Anonymous No.12618291]

>>12618227

>https://en.wikipedia.org/wiki/Lambda_calculus

Here they make the explicit example that
[math]\lambda x.x^2+2 [/math]
is the abstraction of
[math] f(x)=x^2+2 [/math]
and is a definition of the function. Since lambda calculus is just a way to express computation, I don't see many discrepancies in what you're asking. Abstract CS anons may provide better answers.

[Anonymous No.12618423]

Does there exist a theorem that has infinitely many ways of proving it? Is there a way of measuring the complexity of a theorem? If so, has anyone found out which theorem is the most complex? Is there a theoretical limit on how complex a theorem can become? These metamath questions fascinate me.

[Anonymous No.12618429]

>>12618423
Maybe post in /mg/ or a dedicated logic forum elsewhere, nobody here understands metamath.

[Anonymous No.12618480]

>>12618423
>Is there a way of measuring the complexity of a theorem?

probably its length

[Anonymous No.12618527]

>>12618480
not necessarily true. It can be a lot of grunt work and be super longer but not necessarily complex

[Anonymous No.12618537]

>>12618527

i don't think there can be any measure of complexity other than its length, as expressed in a given theory.

[Anonymous No.12618634]

>>12618227
In both math and CS, expressions don't have a fixed "meaning" (what's the meaning of [math]\frac{dy}{dx}= \frac{y}{x}[/math], for example?) but can be interpreted similarly or differently according to the context you care about.
But to answer your intended question, no they are not "exactly the same thing" because the lambda calculus can be realized as a reflexive object in a cartesian closed category, which (by a simple cardinality argument) is not the same as application of mathematical functions.

[Anonymous No.12618644]

>>12618423
Closely related to your question is the Kleene-Mostowski arithmetical hierarchy (google it). If you don't have any solid background in mathematical logic and computability theory, then odds are you'll find even the basic wiki entry on the subject to be total gibberish. In that case, try picking up some introductory text about these fields.
If that sounds like too much of a burden, and your aim is rather to develop an understanding of these 'meta' subjects at the pop-science level, then I highly recommend D. Hofstadter's "Godel, Escher, Bach". It's a wonderful book.

----------------------

On an unrelated note, my own stupid question: Suppose [math]f: \mathbb{R} \to \mathbb{R}[/math] is smooth. Conceptually speaking, should one think of the derivative of [math]f[/math] as [math]\nabla f[/math] or as [math]\operatorname{div}{f}[/math]? (Seeing as the notions of gradient and divergence coincide in 1D, but differ in higher dimensions, the question makes sense IMHO)

[Anonymous No.12618657]

>>12618121
Is it possible to look back in time by travelling at relativistic speeds with a technologically advanced telescope or whatever and leaving that speed at a point where light travelling from neolithic earth would only just now reach, then look back at earth?

[Anonymous No.12618663]

>>12618644
derivative at x = differential at x, i.e. the unique linear map df such that

f(x+h) = f(x) + df(h) + o(h)

[Anonymous No.12618673]

[Biology/Medicine]

I've always had this thing where I feel like my muscles never relax.
When I sleep it's like a pause button, not a reset button.

When I went to draw blood one day, the nurse said to relax my arm, but when I tried she said I wasn't relaxing.
> bruh.jpg
So I had to "force" my arm down to keep it straight so she could draw blood, she mentioned I had "something something" and I better tell my doctor about it, but I forgot what It was because I was trying to keep myself from passing out.

What can It be? The only times I've ever felt relaxed was during my two surgeries when I was under anaesthesia and when I tried some sleeping medicine from my ex, which was Stilnoct/Ambien.

[Anonymous No.12618689]

>>12618423
>>12618644
...let me just add the bottom line, in case you find the wiki entry on the arithmetical hierarchy to be unreadable: A standard measure for the complexity of a formula [math]\phi[/math] is the minimal amount of quantifier alternations needed in order to write a formula that's logically equivalent to [math]\phi[/math]. Quantifier alternation means switching between [math]\forall, \exists[/math]. For that matter, the statement "for all [math]\epsilon > 0[/math] there exists a [math]\delta > 0[/math] such that..." is more complex than "for all [math]\epsilon>0[/math], such and such holds".

[Anonymous No.12618856]

O finitary and logically sound scholars, is interval arithmetic still good for analysis? The author says he uses neither cauchy nor dedekind constructions, although there's some shit on the former later in the book.

[Anonymous No.12618868]

>>12618673
Myotonic dystrophy? Myoclonus?

[Anonymous No.12618902]

i really like /sci/ but i didn't major in science and really don't know anything past high school level and college general electives. is it okay if i still lurk here?

[Anonymous No.12618914]

>>12618902
What's you're IQ

[Anonymous No.12618916]

>>12618868
Don't really experience Myoclonus at all.

And Myotonic Dystrophy is unlikely considering I can have children and I daily put myself under strenuous exercise. It's just that I am never able to relax, so the part with "...Muscles often contract and are unable to relax" is the only part that's fitting.

Thanks for the suggestions though.

[Anonymous No.12618935]

Why not?

[Anonymous No.12618945]

>>12618916
Do you have a family history of Huntington's?
I'd say just see a doc. It's too hard trying to diagnose ppl online without using a phone call or zoom

[Anonymous No.12618948]

>>12618914
i have no idea really. how do i find out? do i contact my old schools? I feel like they made us take IQ tests as kids.

[Anonymous No.12618953]

>>12618948
he's trolling you

[Anonymous No.12618955]

Repost from math general.
i need help on a calculus problem. you dont have to give me the answer but if someone could help me get started. its a max/min problem with lagrange multipliers. I can visualize the problem, its a square on the curve but what would that make the constraint equation? its some kind of multi-parabola looking thing.

[Anonymous No.12618956]

>>12618945
No Huntington's in my family, only genetic stuff we've had is an inclination towards depression.

Yeah, I know, but cheer's for trying to answer it. I've been to a lot of doctors over the years but they've just said "It's stress/anxiety" but... I am not stressed about anything nor do I worry about stuff so.

[Anonymous No.12618965]

>>12618956
Only other thing I could think of is psychomotor retardation/leaden paralysis with your history of depression.
Sorry just a med student thinking. Hope you get some good help anon.

[Anonymous No.12618970]

>>12618965
Maybe, who knows. The medical world is truly a wonder of unknowns.

But I appreciate you trying at least, guess I'll just go bother my doctor about it once again.

[Anonymous No.12618979]

>>12618970
Get an EMG for sure though

[Anonymous No.12618982]

>>12618979
Never taken one, will bring it up. Cheers

[Anonymous No.12618983]

>>12618935
You can't know the derivative with respect to time of the expectation of [math]x[/math], because we only have the wave at [math]t=0[/math].

Use
[math]\mathbb{E}[p]=-i\hbar \int_{\mathbb{R}}\Psi^*(x,0)\frac{\partial}{\partial x}\Psi(x,0)dx[/math]

[Anonymous No.12618986]

>>12618948
>took an IQ test
Failed, your IQ wave function has collapsed, get out

[Anonymous No.12619011]

>>12618983
thanks friend.

[Anonymous No.12619068]

>>12618955
Break the problem up into 4 sections corresponding to each of the vertices, then on each vertex you are maximizing [math] f : R^2 \to R [/math] subject to 4 constraint equations [math] g_i : R^2 \to R [/math] such that [math] g_1 (x,1) = 0 [/math] on the vertex between (-1,1) and (1,1), [math] g_2 (-1,y) = 0 [/math] on the vertex between (-1,-1) and (-1,1) and so on for each of the vertices. You could for instance, pick [math] g_1 (x,y) = y - 1 [/math] on the the vertex between (-1,1) and (1,1)

[Anonymous No.12619299]

[Biology/Medicine]

i had meningitis and lyme disease in the last 3 years. could these have an impact on my gallbladder and (thin) blood?

[Anonymous No.12619387]

>>12619299
Yeah. There’s a condition called Waterhouse–Friderichsen syndrome and if you had septicemia the bacteria could inoculate your gallbladder and proliferate there.

[Anonymous No.12619454]

>>12619387
thank you, anon.
this sounds really dangerous. is there anything i can do?

[Anonymous No.12619472]

>>12619454
Whenever you have symptoms of pain in your right upper part of your abdomen, fever, and/or yellowing of your skin go to a doc ASAP and get a RUQ ultrasound. If it shows nothing ask for a HIDA scan.
Otherwise don’t take blood thinners like aspirin or warfarin unless necessary. Consult a doc first about what you need to take tho.

[Anonymous No.12619512]

>>12619472
thank you very much. im gonna go on a RUQ ultrasound to a self-funding doctor or whatever you call that. i will get an appointment much faster and its not that expensive.
i get pain in the area of my gallbladder every week.

[Anonymous No.12619516]

>>12619512
Yeah then def go and ask for that. If it comes up negative, ask for a HIDA scan. Pronounced hi-duh.
Hope it helps

[Anonymous No.12619551]

>Please include a culture of inclusion statement that best describes how you believe your unique experiences and/or perspectives would help contribute to advancing a culture of diversity and inclusion at [uni].
so i tell them im gay, right?

[Anonymous No.12619563]

>>12619516
thanks bro

[Anonymous No.12619693]

>>12619551
no, trans is a better choice. They will never know

[Anonymous No.12620219]

A job I'm applying for wants me to include "my contributions to diversity inclusion" in my cover letter
I really don't know what to write
Do you think it's enough that I'm black?

[Anonymous No.12620359]

How can I prove that this is decreasing for x>0? Showing that the derivative has no solutions would be enough but I can't figure out how to do that.

[Anonymous No.12620367]

>>12620359
>Showing that the derivative has no solutions would be enough
I believe you mean the derivative is negative for x>0

[Anonymous No.12620370]

>>12620367
No solutions + continuous = negative
Whichever is easier I guess

[Anonymous No.12620416]

Would nickel-titanium make a good cathode to produce chlorates through electrolysis? I work in the dental tool industry so there’s no shortage of scrap pieces of NiTi wire that won’t be missed.

[Anonymous No.12620433]

You can't split the fraction into two terms since dt isn't inside the radical so this is wrong right?

[Anonymous No.12620436]

>>12620433
The dt is squared so it’s fine

[Anonymous No.12620449]

>>12620436
Ah I see it now, thanks

[Anonymous No.12620706]

>>12620449
Np

[Anonymous No.12620720]

>come to /sqt/
>answer questions
>get thanks and nice conversation
>decide to check rest of /sci/
>it’s filled with pseudoscience and misinformation
>everyone just insulting each other
Why is it this way

[Anonymous No.12620791]

>>12620359

[math] \lim_{x \to \infty}x(e^{1/x}-1)=\lim_{x \to \infty}\frac{e^{1/x}-1}{x^{-1}}=\lim_{x \to \infty}\frac{e^{1/x}}{x^2}\frac{1}{x^{-2}}=1 [/math]

[math]x(e^{1/x}-1)>1 \Rightarrow (e^{1/x}-1)>1/x \Rightarrow (e^{y}-1)>y[/math]

Which is true for all y>0. I think this is sufficient to show that the function is at least eventually decreasing.

[Anonymous No.12620851]

Ok this i what i found about the proof of the uniform convergence of the complex exponential function [math]\exp(z)[/math]. I want to know about its uniform convergence beacause it's needed to prove the Euler's formula [math]\exp(ix)=\cos(x)+i\sen(x)[/math] and that the Cauchy Product yields [math]\exp(zw)=\exp(z)+\exp(w)[/math].

I found that its pointwise convergence is not hard to show, using the ratio test for series of complex numbers. To show the ratio test one uses the geometric series convergence.

Next, one needs to show that is uniformly convergent and this is reached using the Weierstrass M-test. If one applies this test to [math]\exp(z)[\math] for z in bounded sets of the complex plane one finds the larger disk that contains such set and taking its radius, together with some inequalities it boils down to the ratio test on the resulting M-series. Thus the exponential function not only pointwise convergent in the entire complex plane but also uniformly convergent for every bounded set (how does this allow one to rearrange the series to show Euler's formula or find the Cauchy product)? .

I have to prove:
-Geometric series convergence
-Ratio test theorem
-Weierstrass M-test theorem

The stupid question that don't deserve its own thread is if this is the most elementary but rigorous proof for the full definition of the exponential function?

[Anonymous No.12620877]

>>12620791
>I think this is sufficient to show that the function is at least eventually decreasing.
Nevermind, that's not necessarily true.

[Anonymous No.12620885]

>>12620851
>https://math.stackexchange.com/questions/460377/is-exponential-function-analytic-over-all-complex-numbers

[Anonymous No.12620917]

Solving Dirichlet problem for 2D regarding the plane excluding a R radius circle centered at the origin using potential theory. Is the solution supposed to come out the same as when taking only said circle as my domain?

[Anonymous No.12620951]

>>12620885
>Cauchy-Hadamard theorem
>Abel's Theorem
I explained why i can't use those results. Because i can't prove them, but maybe i can hope to understand Weierstrass M-test and ratio test proofs. Is there another way?

[Anonymous No.12620968]

Have I answered this question the right way?
You rearrange the equation to [math]t = \frac{ \ln{ \left( \frac{N} {N_{0}} \right)}} {\alpha} [/math] and then simply you just have to recognize that the population will be double when the fraction in the log is equal to 2? it's the correct answer but i'm just wondering if my method is right

[Anonymous No.12620971]

>>12620968
Yeah you did it right

[Anonymous No.12620989]

>>12620971
thanks

[Anonymous No.12620994]

>>12620989
Np. Good job

[Anonymous No.12621162]

What causes pressure on my femoral nerves besides sitting?
I think I have early symptoms of femoral nerve entrapment ,makes sense to me as well because I'm the kind of nerd retard that sits on his ass for hours.
I want to know more activities that cause this so as to avoid them.
I've changed my laptop setup ,I stand up when using it now.

[Anonymous No.12621303]

>>12620359
I think I figured this out. [math]\lim_{x\to\infty} f'(x) = 0[/math] and [math]f''(x) = \frac{\sqrt[x]{e}}{x^3} > 0[/math] for [math]x > 0[/math], which means that [math]f'(x) < 0[/math] since [math]f'(x)[/math] is continuous.

[Anonymous No.12621797]

What degree would you recommend for someone who can only take online classes?
I'm interested in going to school for a long duration of my life. I'm mainly interested in the medical field centering around immunology and "finding a cure". I'll be able to go to school in person in 5-6 years.

[Anonymous No.12621889]

How to solve this?

[math]
\frac{dx}{dt} = -\frac{iE}{\hbar}x
[/math]

Why does the solution involve e?

[Anonymous No.12621916]

>>12621889
Rewrite the equation such that $dx$ is on one side and $dt$ is on the other. Then integrate.

Also, if the change of a function depends linearly on the function itself, the function is an exponential function, just think of exponential decay/growth. Remember this, this is very useful.

[Anonymous No.12621955]

>>12621916
Thanks I think I got it... hardest part was figuring out that dx/x just means 1/x dx lmao
[math]
\frac{dx}{dt} = -\frac{iE}{\hbar}x \\

\frac{dx}{x} = -\frac{iE}{\hbar}dt \\

\int \frac{1}{x} dx = \int -\frac{iE}{\hbar}dt \\

\ln x = -\frac{iE}{\hbar}t + c \\

x = e^{-\frac{iE}{\hbar}} e^c
[/math]

[Anonymous No.12621996]

>>12621955
Well done anon!

[Anonymous No.12622097]

What is it like to defend your thesis? I'm defending my (masters') thesis next week and, although I'm fairly certain of my knowledge in my own research and know two out of four members of the committe, I'm quite nervous about the questions they'll ask later. They are all close friends or former students of my supervisor, but I'm not sure what kind of questions they'll ask afterwards. Any tips?

[Anonymous No.12622117]

>>12622097
master's dissertations are never challenged by the committee. At most, they will ask you to explain some things more in depth after your initial speech. If they think you made a mistake or are being inaccurate, they will flat out tell you, but they won't judge you (it would be a thing between them and your advisor). You'll be 100% fine.

[Anonymous No.12622163]

>>12622117
thank you anon. I've already spotted a few typing errors in my text after I submitted it so I imagine they're going to mention that and likely find more (one is in the statement of the most important theorem, kek). hopefully all goes well indeed.

[Anonymous No.12622207]

>>12622163
If the typos are obvious it is highly unlikely they will bring them up to criticize you, so don't worry about that.

[Anonymous No.12622248]

why the negative sign?

F = -V'(x)

[Anonymous No.12622272]

>>12622248
So that you can set the energy reference to the smallest positive value of 0.
The other end isn't naturally bounded.

[Anonymous No.12622361]

Hello I study an IT field but for some unclear reason I have this subject of.. Mechanics and motion. Not only does it not help me in any way, not even remotely, in my future job, mechanics are also my weak subject and I'd rather take electric stuff or some shit.

Anyway say I have an exam in it and I come asking these questions to be solved (10 max) will i get help here or will I get fucked?

[Anonymous No.12622364]

>>12620720
Nice people go out of their way to help people, and find threads dedicated to help. Trolls avoid threads like this.

[Anonymous No.12622398]

>>10318197
Question from /his/
-This is an alternative proposal to fix the problems with a vacuum blimp.

What if instead of a full vacuum it was mostly a vacuum with an inert easy to acquire gas like nitrogen? Would that work?

[Anonymous No.12622402]

>>12622398
>>>/his/10315875

[Anonymous No.12622410]

Maybe a general education question but I'll try.
I'm finishing high school after many, many years of battling with depression and stuff. So I can finally go to college/university.

But I have no idea what to study, I want to study history or teaching, but that's 6/5 years of studying. The problem there is teaching includes languages and grammar which I absolutely don't understand. One of the reasons why I haven't graduated earlier is because I fail to understand Norwegian and German grammar. Verbs, Subjective, Adjectives etc It's all a mess.

I've looked at economics but I relatively suck at math too, so I don't think It's for me? I find economics fascinating but once It starts with math formulas and stuff I'm just unable to understand it.

Any ideas?

[Anonymous No.12622473]

>>12622410
>I find economics fascinating but once It starts with math formulas and stuff I'm just unable to understand it.

you won't make it with this mindset. Either you embrace math, learn to appreciate it and fill in all your gaps, or you're better off going for a liberal arts degree. Modern econ is straight, hardcore math, very far from demand-supply curves you may have seen as an intro. Well, that's unadulterated BS. So make your life choice anon.

[Anonymous No.12622488]

>>12622473
I've gotten better at math, I've really trying to put myself into it. I've gone from a 2/E to a 5/B. But once It starts getting harder than algebra I begin to fall off, the numbers and formulas just get messy. The hardest math I've successfully done is stuff with con, tan, sin.
But I appreciate the description of modern econ.

[Anonymous No.12622504]

Does every diagonalizable matrix only have one eigenbasis? Eg if I have a matrix with linearly independent columns and it is diagonalizable then does it have two different basis', one eigen and the lin indep one?

[Anonymous No.12622515]

>>12622488
>once It starts getting harder than algebra I begin to fall off
I don't believe that beyond trig functions you really break down. You probably had poor mentors and poor life examples in this regard. Please correct me if I'm wrong: you're one of those students who just want to have everything under their control when studying math. That's a recipe for disaster. You have to change your mindset.

IQ caps are effective only at really highest levels of math and physics (the hardest econ is not even close). Everything below is attainable if you're not a retard. I think your problem is in mentoring/teachers.

[Anonymous No.12622516]

>>12618121
Fff

[Anonymous No.12622528]

>>12622515
You got me there, I want to be absolutely 100% sure when studying something, especially math since one error can screw you over pretty easily.

It may also have been something with me having depression for nearly 10 years in my youth and IRL issues keeping me from stuff. But your words are encouraging, appreciate it anon.

Think I'll check some stuff out.

[Anonymous No.12622530]

>>12622361
you can ask but theres no guarantee anyone will answer. Also if its elementary classical mechanics its really not that bad. Theres whole channels on youtube dedicated to explaining it simply, you really need minimal effort to pass it.

[Anonymous No.12622533]

>>12622528
I don't think you can do that alone. If you can afford it, get private lessons from people who prep high schoolers for college, maybe highly rated ones. Ask friends that are mathier than you. Post questions on /sci/.

[Anonymous No.12622538]

>>12622533
Thanks, I really, really appreciate it anon. Will heed your words.

[Anonymous No.12622636]

>>12622538

not him, and i do think you can do it alone. that may actually be the best way so you can relax and think about things without trying to keep up with a tutor.

trig isn't super important right off the bat and i would ignore it for a while. it's unfortunate that high schools teach it rather than something like logic or very basic analysis, which one would need if they ever wanted to understand sin,cos,tan as anything other than black boxes that run on dark magic and spit out angles.

high schools are terrible at teaching math and you should forget any conceptions you have about math or your ability/inability to understand it. what exactly do you have trouble with?

[Anonymous No.12622666]

>>12622636
It's just when formulas/lengthier equations come up, I tried "Physics 1" as It's called during my second year of high school and I failed miserably since I had to recall and remember so many small numbers, how to convert things etc.

I've generally had a problem with understanding math, I had a test about functions three weeks ago where I had to plot stuff into a program and I struggled for hours to understand how to set up a basic function like "T(x) = Function[4+3*x,0,5]" in the program.

Even when looking at a graph and being told to "Find a function for this graph" made me totally miserable over not understanding it.
Even if the answer was as simple as: "f(x)=-1.5x+3"

[Anonymous No.12622744]

>>12622272
Can you explain that again but this time pretend I'm retarded.

[Anonymous No.12622829]

>>12622666
>"Find a function for this graph"

in high school, this probably only involves polynomial functions. you've probably heard "slope" and "intercept" before, but more generally you can think of it as finding the coefficients of a polynomial f(x) = c_n x^n + ... + c_1 x^1 + c_0 x^0.

you're looking for the c's. x^0 is just 1, so that's where the constant term comes in. if you have at least n+1 data points, you can solve for the n+1 coefficients (including c_0). in your case, it's a linear function, a polynomial of degree 1. so you pick any two data points (for f(x) and x). then you solve for c_0 in one of the two equations. you will have c_1 on the other side, and so plug that expression in for c_0 in the other equation. then you have an equation whose only (unknown) coefficient is c_1. you solve to get an actual number for c_1. at this point c_1 is known and you can substitute its value, and you have two equations whose only unknown is c_0. pick one and solve for c_0. you'll notice that c_0 is actually the point on the y-axis that the line crosses, which is why they call it a "y-intercept", but i don't think such tricks are useful until you actually know what's going on.

for higher degree polynomials it works the same way, but it's a bit more work

[Anonymous No.12622852]

>>12622829
cont.

i don't envy the job of a high school teacher though. most people probably don't, so i'd try to work it out on your own rather than hire a tutor.

[Anonymous No.12622889]

>>12622248
It's necessary to preserve the conservation of energy.

[Anonymous No.12622916]

>>12622410
>>12622473
economics is not a science in the first place and the math is a facade by atheists addicted to popsci to pass it as scientific.

[Anonymous No.12622921]

>>12622410
go into geology, the only maths you need is HS exponential stuff fro carbon dating

[Anonymous No.12622925]

>>12622829
Thanks.

>>12622916
Uuh, yes. Ahaha, I guess.

>>12622921
Few jobs here with geology though.

[Anonymous No.12622927]

>>12622097
for a phd, they ask what part was hard and you have to explain why and tell the proof in details.

[Anonymous No.12622932]

>>12620219
>>Do you think it's enough that I'm black?
that's the golden ticket

[Anonymous No.12622933]

>>12622916
>economics is not a science
True
>the math is a facade
No, in fact mathematical rigor is the only way to make an economic model legitimate, since you can't use scientific methods to model economics. This is why modern econ involves pretty crazy levels of math (still not close to physics though).

[Anonymous No.12622947]

>>12622933
mathematical models ruined economics. you can't predict the future based on the past when it comes to complex systems like economic ones. that's why it's not a science - because two experiments are never the same. yet mathematical models like the black scholes model are used, giving people the delusion that they work.

[Anonymous No.12622959]

>>12620219
>"my contributions to diversity inclusion"

is that what it reads verbatim? what kind of question even is that? contributions to whom? when? where? of what?

[Anonymous No.12622969]

>>12622504
Since constant mulitiples of eigenvectors are eigenvectors in the same eigenspace, there is more than one eigenbasis.

[Anonymous No.12623044]

>>12622248
Take surface gravity. If the potential increases like mgh, the derivative is constant, mg. The force you experience should be pointing down for you to go to the state of lowest energy; that's what the minus sign is for.

[Anonymous No.12623054]

>>12622947
black scholes is not economics, neither it is used in practice because it barely tries to model agent behavior and relies on huge assumptions that are proven to be incorrect by statistical analysis. utility maximization in dynamic portfolio choice is closer to economics, but in the same context.

[Anonymous No.12623088]

>>12622959
>"Your past or proposed contributions to diversity, equity, and inclusion."

[Anonymous No.12623152]

>>12623088
Isn't this illegal? Evidently not, but how do they get away with it? I thought you couldn't hire based on race whether your race is a privileged or less privileged one.

[Anonymous No.12623208]

>>12623152
I think it's more like whoever wrote the job application really doesn't want anyone remotely right wing hired, so they force you to mention how much you support BLM or something.

[Anonymous No.12623550]

can i say this is the definition of a sphere [math]E[/math] of center [math]C = (x_0,y_0,z_0)[/math] and radius [math]D[/math]?

[Anonymous No.12623555]

>>12623550
It's missing a comma but otherwise yes.

[Anonymous No.12623601]

>>12623555
a comma where? I know it's not as precise as it could be, but if it's good enough then I'm going with it. should I switch the | for a comma then?

[Anonymous No.12623617]

>>12623550
[math]E=\{\mathbf{x} \in \mathbb{R}^n|d(\mathbf{x},\mathbf{x_0})=D\}[/math]

[Anonymous No.12623619]

>>12623617
obv in your case n=3

[Anonymous No.12623626]

>>12623617
>>12623619
can't you have imaginary spheres though? that's what I was trying to avoid because I can't into imaginary stuff, so I wasn't so sure as to the [math]R^3[/math]. this is probably a retarded question, I want to learn complex numbers but I just don't have the time to before this assignment is due

[Need honest advice No.12623640]

Anyone have a roadmap to becoming a self taught rain man mathematics gigga-nigga. I finally have a decent job that gives me enough free time to learn what I want and I want to get a phd in
pure math without going to school. I prefer textbooks over udemy.

[Anonymous No.12623738]

>>12623601
No, the comma separates the arguments of the
[math]d[/math] function.

[Anonymous No.12623760]

>>12618121
My school give us the past end of year exams from 2000 to 2020. From the questions on each exam I can find these things:
1. Which topics appear frequently according to year. (older the exams, the less relevant they are)
2. How many students got how many marks for each questions (maybe topics students score low on appear again)

The exam is separated into MC and short answer. What is the best way to set up a spreadsheet/graph to slightly predict what will be in the next exam.

[Anonymous No.12623890]

>>12623738
oh you're right, thanks!

[Anonymous No.12624252]

>>12623626
distance function is always real and non-negative, so you don't run into any issues with complex numbers

[Anonymous No.12624257]

>>12623152
wouldn't be surprised if it no longer is in the near future, hell the recent prop 16 thing in Cali shows just how close to reality this is

[Anonymous No.12624272]

Would you say that everyone capable should know some math and science even it may not be directly related to their career at the moment?

[Anonymous No.12624314]

>>12624272
yes

[Anonymous No.12624396]

>>12624272
yes

[Anonymous No.12624516]

>>12624272
no

[Anonymous No.12624577]

i need to learn calculus, is this chart meme yes or no?

[Need honest advice No.12624613]

>>12623640
can anyone answer this?

[Anonymous No.12624626]

>>12624577
That depends on how much time you have and what you want to use calculus for. Do you want to just do calculations with calculus? Or do you want to know everything there is to know about it?

[Anonymous No.12624641]

>>12624626
i want to apply to a masters in economics. but i need a solid grasp of calculus-linearalgebra-statistics. I want to learn all of that in 2 years max.

[Anonymous No.12624654]

Is Khan Academy good? I have at times found myself stymied by the grading/credit system.

[Anonymous No.12624671]

>>12624641
Then the chart would probably be a meme. You won't be focused on proving theorems. The calculus books (Apostol/Spivak) are good ones though. Apostol is probably better for more applied things. I think he covers linear algebra in volume two as well.
If you really just want to learn calculus and don't care about all the theory and such use any book, look at the MIT OCW they have videos and a syllabus for linear algebra and calculus.

[Anonymous No.12624681]

>>12624577
Meme.
Do pic related instead.

[Anonymous No.12624689]

>>12624681
Lang and Spivak, what a duo. They are like opposite ends of the spectrum. Which spectrum? I don't know, but some spectrum.

[Anonymous No.12624690]

>>12624577
Read one Proof book
Read Enderton if you want more practice
Read Basic Mathematics if you need to review/learn precalculus
Read Courant&John for Calculus. Less dry and more applications

[Anonymous No.12624693]

>>12624681
ok bro many thanks.

[Anonymous No.12624696]

>>12624671
Idk if theory would be useful if i try to follow a phd path.

[Anonymous No.12624701]

>>12624681
should i add proof book too?

[Anonymous No.12624723]

>>12624701
No.

[Anonymous No.12624724]

>>12624696
Then you want Spivak or Apostol for your calculus, that is true. The Polya How to solve it book from that chart is good too, for problems from any discipline. Hoffman & Kunze is a good application & theory linear algebra book. If you have trouble with proofs pick up a book for that, but otherwise just practice. You can fill in missing steps in the proofs a book gives, and do problems and you'll get better with time.

[Anonymous No.12624755]

>>12624724
thanks bro

[Anonymous No.12624876]

I cant seem to find a formula for the average of an interval on the normal distribution. Someone has to have done this by now. Is this well known or do I need to break out the abacus?

[Anonymous No.12624887]

>>12624272
no, lana Rhodes does not need to have a working knowledge of calc.

[Anonymous No.12624924]

>>12624689
the autism spectrum, of course

[Anonymous No.12625011]

Is this saying we gained a dimension in the transformation?

[Anonymous No.12625219]

>>12625011
A maps R^3->R^4. You aren't gaining a dimension in the topological sense; the rank of A can't be any greater than 3, so the image of R^3 under A will be a 3-dimensional (or less) subspace of R^4.

[Anonymous No.12625386]

>>12625011
this is just saying how to match the dimensions of the matrix w/ the dimensions of the domain and codomain

[Anonymous No.12625554]

>>12624876
It's well known. You can derive it easily by integration by substitution

[Anonymous No.12625556]

>>12625554
Another hint: look at the first derivative of the Gaussian density. Looks quite good right?

[Anonymous No.12625563]

>>12624755
Bro don't listen to the spergs who suggest Spivak to fucking learn calculus lmao, Spivak is a book for people who already know calculus. Same for Rudin in analysis, they are a meme. Your first approach to calc has to be way smoother and intuitive. Look for intro books with plenty of quick and easy plug-chug exercises, then move onto better shit

[Anonymous No.12625582]

>>12625563
I suggested the regular calculus stuff, like MIT OCW which is similar to Stewart or Edwards calculus. He asked for stuff with more theory which is why I suggested what I did.

[Anonymous No.12625704]

I am being given a couple different ranges (0 to 100, 101 to 200, etc) for a variable X, along with the frequency for each range.

I have calculated the mean range, but how do I calculate the standard deviation for the mean range?

[Anonymous No.12625990]

If you boil hydrochloric acid (HCl + water?) down to nothing are you left with an empty boiling tube? ie the water and HCl simply evaporate? I'm extracting opium from poppy straw and read that sometime acid is added to increase the solubility of the morphine, but I don't want to add citric acid or something because when I evaporate the mixture the citrates will remain

[Anonymous No.12626056]

>>12625990
why wouldn't it evaporate?

but then, putting aside the fact that you're boiling an potent acid, you'll then have to manage with the fumes that come from evaporating (hint: it's not fun breathing that stuff in)

[Anonymous No.12626088]

Can someone tell me if I'm retarded or need to take a step back and learn some math.

Working through this book and I'm about 50 pages in and don't understand what's going on. I know basic math - can do algebra, integration/differentiation, and know about vectors and complex numbers - but here I have no idea how the author goes from one step to the next.

Do I need more math or am I too dumb for qm?

[Anonymous No.12626123]

>>12626088
You might know the basics but knowing all those topics to an undergrad level is typically what you need to start on QM.

Is there any particular example you can show that you didn't understand?

[Anonymous No.12626160]

>>12626123
So far I understand that to solve the Schrödinger equation you separate the time evolution component from the time-independent SE, and if you solve them both you get this

[math]\Psi_1(x, t) = \psi_1(x)e^{-iE t/\hbar}[/math]

That's pretty simple and managed to derive this. Then on the next page it starts talking about the Hamiltonian operator and energy states and infinite linear combinations and absorbing constants into psi

[math]
\hat H\psi = E\psi \\

\Psi(x, t) = \sum_{n = 1}^{\infty}c_n\psi_n(x)e^{-iE_n t/\hbar}
[/math]

I've read this shit a dozen times and I have zero intuition about what's going on or how the author is getting there

[Anonymous No.12626215]

>>12626160
That is more a mixture of physics and maths. The last line is saying that the system wavefunction is a superposition (combination) of each of the possible individual energy levels, and their associated wave functions, with some scaling probability factor (c_n) for each. So if you then applied the Hamiltonian operator on that sum you would get the energy (E) of the total system.

That is all related to superposition's, eigenvalues and eigenvectors which will be covered elsewhere in that book if you haven't reached those chapters already.

[Anonymous No.12626246]

>>12626215
>the system wavefunction is a superposition (combination) of each of the possible individual energy levels, and their associated wave functions
I've read that in spin experiments the photons are in a superposition of spin up and spin down states, and so you can represent the wave as a linear combination of the spin states and their probability amplitudes. How does this relate to the infinite collection of energy states here? Thanks btw

[Anonymous No.12626250]

>>12626160
>I've read this shit a dozen times and I have zero intuition about what's going on or how the author is getting there
Read Miles Mathis and you won't give a fuck.

[Anonymous No.12626267]

>>12626250
Lmao this crank is next level

[Anonymous No.12626275]

>>12626246
An example of a collection of infinite states would be the electron of the hydrogen atom. The time evolution of the total wavefunction would be the normalised combination of each of the possible energy levels and their associate eigenstates.

[Anonymous No.12626340]

If B gains another proton wouldnt that make $B^(2+)$, shouldnt B lose a proton?

[Anonymous No.12626343]

>>12626088
I similarly found his text to be quite jumpy at times. If you have a proper background in math and tend to favour more rigour I'd recommend J.J Sakurai's Modern Quantum Mechanics as a better substitute. Its a lot more advanced but I find it easier to follow

[Anonymous No.12626362]

>>12626343
I like Sakurai too. Though I'm going to throw in a suggestion for Shankar, it has some good parts to it. Plus, it's very self contained, it has all the material you need in it which may solve the issue at hand.
I know Griffiths is usually considered the 'easiest' but I never liked it... used it for my first course on QM.

[Anonymous No.12626397]

I've seen a book recommendation flow chart for math and philosophy posted here.
White background with rectangles, i think.
Anyone has it?

[Anonymous No.12626413]

>>12626343
>>12626362
Sakurai was never finished but Shankar is both complete and more readable.

[Anonymous No.12626537]

>>12626267
Just read his paper on superposition. Then you'll know.

[Anonymous No.12626646]

>>12618121
Are there any geodesists or surveyors in this thread? I do not have a background in geodesy and I am trying to understand the fundamental equations of physical geodesy, namely Stokes' formulation for the geoid undulation and related formulas.

I can't find any good or intuitive explanations of what the formulas actually mean and why we are applying them. Furthermore, I don't really have a good understanding of what the "Stokes' Function", "Stokes' Kernel", and "Modified Stokes' Kernels" even are. All the references and texts I have just throw the words around without explaining what they are. There are tons of papers and texts out there on the subject, but they are all written at the graduate level or for academics/specialized researchers and do not derive anything from first principles.

I am interested in this because am interested in learning about GPS and global guidance/coordinate systems as well as just physical geodesy and gravity in general. I need to understand positioning systems well and also the specific effects of gravity at all points on earth and I just don't seem to have a great starting point.

I would love some help on this issue. Pic related, my own attempt at visualized EGM 96 using just public data which turned out pretty well. It was a simple enough coding project, but the mathematical and physical basis for geodesy is really proving pretty elusive to me.

My background is in physics if that matters.

[Anonymous No.12626967]

Why do I feel like I don't know what I should be doing in my Ph. D.? I've got a lab with all the equipment to do a variety of experiments. Is this choice paralysis? It doesn't help that my upperclassman who I share the lab with is incredibly anal. If I so much as set down tweezers in the wrong spot I will be yelled and swore at.

[Anonymous No.12627154]

I'm week 2 in general chemistry II and how the hell am I supposed to remember all the equations for work, heat, and internal energy? Do I just do practice problems until I start dreaming about chemistry?
I got an A in gen chem I last semester. I feel rather stupid right now.

[Anonymous No.12627206]

If this notion of non-computability hierarchy I came across isn't the usual wikipedia baloney, is it anything like computational complexity hardness classification?

[Anonymous No.12627233]

>>12626362
Can vouch for Shankar, it actually builds up the linear algebra background you need for QM if you're lacking in that department.
I hate Griffith's organization in the first few chapters. Throwing you in the deep end of computations without any understanding of the formalism is utterly detestable. This is "shut up and calculate" mode of thinking at its worst.
The later chapters are OK, and the new edition does improve on some of my gripes, but it's better to just jump ship to another book.

[Anonymous No.12627269]

Is a study that uses longitudal data automatically a longitudal study? I have a study in fron of me that has been done only once but it uses data by a Socio-economic Panel from 2001 to 2012. Is the study I'm reading now a longitudal study by default (because what really matters is the data basis) or is it still a cross-sectional study (since my actual study isn't one that's regularly done)?

[Anonymous No.12627274]

>>12625219
>>12625386
>You aren't gaining a dimension in the topological sense
I thought that's what R^n meant. n was whatever dimension of space you're working in. The image, of course, is still a three dimensional image; there are only three vectors here. Clearly I don't understand codomains and ranges yet, and I hope that's the problem.
Follow up question: A is necessarily a linearly dependent system because there are more vectors than there are coordinates in the vectors, right? With "extra" vectors like this, you have the means to transform any single vector in the system to any other, right? And this could be done with a combination of scaling and vector addition/subtraction.

[Anonymous No.12627281]

>>12627269
It’s longitudinal if it occurs over a time period.
Cross section if one point in time.

[Anonymous No.12627289]

>>12627281
Yes, I know that in general. But the study I am reading isn't done more often than once (cross sectional). It is using annually produced data of a panel though (longitudal).

[Anonymous No.12627295]

>>12627289
Is it a review or metanalysis of a longitudinal study?

[Anonymous No.12627305]

>>12627295
That's what I mean: https://onlinelibrary.wiley.com/doi/abs/10.1002/hec.3199

This study uses data of the British Household Panel Surveys - which would mean it's longitudal. But that study by Künn-Nelen about the effects of commuting has only ever been done once - which would mean it's cross sectional.

[Anonymous No.12627324]

>>12627305
Ok this is a longitudinal retrospective cohort study.
Just because the article is studying a phenomenon at one point in time doesn't change that the data is longitudinal in nature.

[Anonymous No.12627356]

>>12627324
Okay, I got it, thanks a lot!

[Anonymous No.12627383]

>>12627356
No problem. Are you in med school or something?

[Anonymous No.12627396]

>>12627383
No, that's for my Human Resources class of my minor in Business Economics.

[Anonymous No.12627461]

>>12627396
Oh ok. Just remember back in med school we had to identify types of studies based on their data.

[Anonymous No.12627518]

>>12626160
I think that you should first get a grasp on the solution of the heat equation with the usual boundaries (natural, dirichlet and/or neumann). Once you get the math behind it you'll understand it all. It's 100% a math issue.

[Anonymous No.12627525]

>>12627461
I think it has to do with me being kind of more motivated and trying to really UNDERSTAND what a study and a course is about - something that's not really prevalent amongst students of Business Economics...

[Anonymous No.12627558]

>>12627525
Oh that sounds cool. Best of luck anon.

[Anonymous No.12628049]

How do I go about calculating what would happen to an EM wave thats being scattered by a delta scatterer and the effects of another delta scatterer placed x away from the first. What textbooks do I need I get that waves are complex eponentials but how do they interact with scatterers?

[Anonymous No.12628161]

>>12618121
can anyone solve this? ive struggled with this for 2 days now, bruteforcing is way too slow and i cant think of a fast solution

[Anonymous No.12628247]

/sci/bros, I need your guidance.
My semester is starting next week and I'm stressing the fuck out to the point that I cannot have a good dream for the past 4 days. I have three classes that I need textbook recommendations (you don't have to recommend one for all three) for:
1) Linear Algebra
2) Differential Equations
3) Probability and Statistics
Is there any calculus material I need to review before starting any of these classes?

[Anonymous No.12628270]

>>12628247
For the first two I always recommend this site, https://tutorial.math.lamar.edu/..

[Anonymous No.12628288]

>>12628247

I second this suggestion >>12628270, it's a total gem. Probability is quite vast so it all depends on your syllabus and how deep you'll go into the rabbit hole

[Anonymous No.12628376]

>>12628161
I feel like this is about router protocols or general communication protocol. It is kinda ass because queues can't be reordered so you are deciding A or B. There is certainly sources out there to help you online.
Translate it another way: the cars are messages and they have some bit length. Both sides look at their message buffer and determine who should send first to clear the buffers soonest.
I am guessing the ten second clear interval is the real trick in this problem and I think the solution is about using fast cars to minimize that delay. Probably something along the lines of longest message is always first, but with a trade off for getting the shortest message to the front of a line, prioritizing back and forth communications.
Start with simple cases using a small number of vehicles, less than 6. The answer should fall out of that.

[Anonymous No.12628430]

>>12628247
3blue1brown on youtube, essence of calculus and essence of linear algebra, you dont have to understand everything, but for me especially the calculus one helped me to get a deeper intuition

[Anonymous No.12628482]

I want to describe the motion of two free charged particles on the surface of a two dimensional sphere using the 2 dimensional coulomb force. I can write the free part of the lagrangian but the 2D coulomb potential is logarithmic in r (the distance between the charges) and I can’t figure out what this means on the sphere. Am i supposed to calculate the actual arc length / geodesic on the sphere that connects the two charges and if yes how am i gonna do this?

[Anonymous No.12628543]

Did Albert Einstein plagarize all his shit?

[Anonymous No.12628549]

>>12628543
No. Why would you think he did?

[Anonymous No.12628551]

>>12628549
He worked in a patent office

[Anonymous No.12628559]

>>12628551
You don't patent physics theories.

[Anonymous No.12628566]

>>12628559
not with that attitude you cant

[Anonymous No.12628590]

How do I become competant in maths when I have Dyscalculia?

[Anonymous No.12628602]

In Saxon math (3rd grade) my kids just jumped from
>multiply by 1s or 10s
to
>multiply by 7s
it came home as homework but no explanation on HOW we're supposed to do it. We've been talking about x groups of y, so we're just doing 7 x 2 is 7 + 7 so 7 x 3 is 14 + 7 etc. but in no way is the worksheet set up for that.

So my question is in Saxon math is there some special way to multiply by 7 that would put it before multiplying by 2 or 5 for example?

In my day we just memorized the tables, and saxon math is more like I actually did math but this one thing I cannot fathom.

[Anonymous No.12628612]

>>12628590
Good question. All hope may seem lost at that point, but fret not, people before you faced the same problem. For example, you'd typically have difficulty telling whether a number is a prime, even for small values, right? It's fine, we live in modern times, when modern inventions allow even those challenged in some departments to squeeze out the most of their potential, and maybe even achievements unthinkable a mere hundred years ago, like being a mathematician with dyscalculia, are not out of reach.
The amazing modern invention that will alleviate most of your described problems, is known in hacker circles as Category Theory. You may read more on its foundation and development for inspirational figures that were beget with the same troubles as you, yet were recognized as the best of the best of their times. What's important, is that you know that you aren't alone in your misfortune, and certainly not hopeless.

[Anonymous No.12628632]

>>12622410
only one right answer anon. psychology. also ffs don't go to college just because you think you should go to college, that's the road to debt and useless degree.

[Anonymous No.12628640]

>>12628602
What does lesson 56 say?

[Anonymous No.12628650]

>>12623760
Identify each unique question.
Identify each question type.
List these in the 2nd and 1st column.
Mark each subsequent column 2000 to 2020 incrementally, more if there is >1 exam per year.
For each unique exam question tick the year(s) it appeared.
Sort by question type.
Look for patterns, e.g. there is only one question of this type each year, but always one or there is never an exact question repeated sooner than 3 years after it last occurred.
???
profit.

[Anonymous No.12628659]

>>12626967
What is your PhD going to be about?

[Anonymous No.12628661]

>>12627154
you never had to memorize anything before?

[Anonymous No.12628663]

>>12628640
I mean that's the issue, we only have the homework, we don't get the book.

[Anonymous No.12628715]

>>12627274
> I thought that's what R^n meant. n was whatever dimension of space you're working in. The image, of course, is still a three dimensional image; there are only three vectors here. Clearly I don't understand codomains and ranges yet, and I hope that's the problem.

Consider the case where A is 3x2, i.e. it maps R^2->R^3, as that case should be easier to visualise. For any 2D vector x, the 3D vector Ax lies in the same plane as the columns of A, i.e. it's transforming R^2 to a plane (a 2D subspace) in R^3. In the 4x3 case, it's transforming R^3 to a 3D subspace of R^4.

> Follow up question: A is necessarily a linearly dependent system because there are more vectors than there are coordinates in the vectors, right?
Because there are more rows than columns.

> With "extra" vectors like this, you have the means to transform any single vector in the system to any other, right? And this could be done with a combination of scaling and vector addition/subtraction.
It means that at least one row can be expressed as a linear combination of the other three.

[Anonymous No.12628725]

>>12628602
Kids can't even bring their textbooks home anymore? What is wrong with schools nowadays?

[Anonymous No.12628734]

Is it normal for someone to cite unpublished articles in their own?

[Anonymous No.12628741]

>>12628612
>Category Theory.
Never heard of it I suppose I will look into this

[Anonymous No.12628744]

>>12628734
I've seen citations to articles that have yet to appear, or things like 'conversation at x conference with y person'. If you mean a citation to 'super secret paper I won't show anyone' then I wouldn't trust it. Just like I don't trust those physics papers that use software they won't let you see.

[Anonymous No.12628766]

>>12628734
It's better than not citing? Aren't there large repositories of not-available-to-the-public papers?

[Anonymous No.12628776]

>>12628725
I'd blame covid, but it's been like this since kindergarten. The books are workbooks, not textbook proper, and if the actual sheets didn't come home occasionally, I'd swear they were just using a single book and pocketing our fees... in any case they used to *always* be actual worksheets from the books and we go the books at the end of the year. I do blame covid for that.

[Anonymous No.12628783]

>>12628776
Well if they don't give you the book or some print out or some website with the info, I'd say the homework can't be done. How are you supposed to know what shitty method they teach math with?
I did a search though and it seems that book is pretty common, you can probably find the method they use if you don't want to start a huge argument with them.

[Anonymous No.12628809]

I haven't done linear algebra in two years, and I can't remember the terms to search anymore.
This is just a participation quiz, and I figured the first two out because I'm not an idiot, and the third using the online tool my prof showed us.
I just don't remember how to solve these things "properly".

[Anonymous No.12628816]

>>12628809
Also, does anyone have good resource for octave to get info about optimizations?
Basically, does anyone know what I should look/search for to review this stuff. The professors review didn't answer my questions, and he uses completely different terms than I recognize.

[Anonymous No.12628823]

>>12628816
Have you tried the docs? It has examples?
https://octave.org/doc/v4.0.0/Optimization.html

[Anonymous No.12628848]

>>12628823
It appears I posted an old version, this is the latest
https://octave.org/doc/v6.1.0/Optimization.html

[Anonymous No.12628874]

>>12628848
>>12628823
To be completely honest the docs didn't really make much sense to me.
I should have mentioned that before. Finding the optimal solution isn't really an issue because of the calc. It's when I have to analyze a systems of equations? My fundamentals are very very lacking, I struggled through calc 1/2 with a C in both. Any guidance with this would be appreciated.

[Anonymous No.12628884]

I'm in a graduate level reactor operator's course, doing research for credit which has me learning to use MCNP on high performance computer cluter, and in probably the best shape of my life. I'm making dreams come true. Why am I still so unhappy, anxious, depressed, and unfulfilled?

[Anonymous No.12628982]

>>12628809
> I can't remember the terms to search anymore.
Linear Programming, Simplex Algorithm

[Anonymous No.12628993]

Which symbol is this? ∑

[Anonymous No.12629102]

>>12628993
Greek capital letter sigma.

[Anonymous No.12629427]

>>12629102
Sigma balls

[Anonymous No.12629576]

So I skipped school a bunch and now am held back into a program to get out of school before my GED I forgot a bunch of my math and the deadlines in 3 days. It's simple Algebra how fucked am I? No I'm not underage just an idiot who put off high school because he was scared of ghetto niggers.

[Anonymous No.12629814]

Visible light passes through water to well to heat it.
Infrared is absorbed so well that cooking heats from the outside in.
Microwaves somehow strike the right balance between the two.

How? And can the same logic be applied to sound waves through a body?

[Anonymous No.12629823]

>>12629576
There's a link above for algebra, algebra isnt too difficult. Start studying right away and you should be fine.

[Anonymous No.12630069]

The energy–momentum tensor for translationally invariant systems encodes three continuity equations. I understand that rate of momentum (= force) is given by a surface integral over stress (thus explaining why those tensor terms are identified as such), but I don't see how this works out for the energy component. Apparently, rate of energy can be calculated by surface-integrating the momentum. This is a relation that I've never seen before, is there a simple way to understand it like with stress?

[Anonymous No.12630087]

>>12630069
four continuity equations*

[Anonymous No.12630100]

"Bell's theory rules out LOCAL hidden variables."

People often say this, as those the existence of non-local hidden variables is significant.

Would we even be able to tell the difference between non-local hidden variables and straightup instant communication?

[Anonymous No.12630252]

>>12629814
what do you mean, sound waves at a particular frequency that would heat up something?

[Anonymous No.12630271]

Does anyone know how to get book that couldn't be found in libgen and zlib, the books name is d-block chemistry Oxford primer no 27 by mark J winter

[Anonymous No.12630292]

>>12630100
I dont think the semantics is of importance here. What is a non-local hidden variable? Would it be stored in the quantum field? It sounds like it would be analogous to another type of law or interaction which would then remove it from the system. The term local here aims to mean specific to an object in a system. As for your second point; communication i.e some signal cannot travel faster than light i.e the fastest signal. The orthodox way of looking at this entanglement phenomena is that the entangled particles share a wave function, the collapse of the wave fuction is instantaneous, think changing x to x^2, the change is instant over the entire domain. In this way you dont violate relativity. It should be noted here though that this is only a mathematical description, the actually mechanics of what is going on behind QM is not yet known, as far as I'm aware anyway.

[Anonymous No.12630299]

>>12618121
>wanting it to be easy
what a cope image, everything comes down to your genetics, especially if you're male. if i was born either female or handsome i wouldn't be contemplating my sucide in my early 20s right now

[Anonymous No.12630315]

>>12630292
By instant communication I mean "spooky action at a distance", which is essentially what non-locality entails.

>Would it be stored in the quantum field? It sounds like it would be analogous to another type of law or interaction which would then remove it from the system

This is my question. How could you ever know the difference between non-locality embedded in a law (i.e. a non-local hidden variable) and non-locality as a simple case of action at a distance?

[Anonymous No.12630357]

>>12630299
>be born with handsome looks
>get repeatedly sexually assaulted and harassed for the first 20 years of my life
>even my mother has said weird shit to me
>feel like shooting myself in the face almost daily

[Anonymous No.12630364]

>>12630357
>humble brag
>woe is me
you're not helping me

[Anonymous No.12630375]

>>12630364
>abloo bloo bloo I have to face unfair hardship
So does everyone else

[Anonymous No.12630391]

>>12630375
>So does everyone else
no, you yourself showed me you have never faced hardship that would genuinely make you suicidal. the sexual drive is the most powerful instinct and you've never experienced it like i have

[Anonymous No.12630470]

>>12630315
Its an interesting question, by non-locality do you mean a unknown or unknowable law that influences all systems? For example it is built into models such as GR without us realizing it but if you would to isolate it it would do something else? I'm not sure I understand what youre trying to say though, should your concept be simple to grasp or is it more nuanced?
>How could you ever know the difference between non-locality embedded in a law (i.e. a non-local hidden variable) and non-locality as a simple case of action at a distance?
Also youll have to explain what a "simple case of action at a distance" is. Do you mean how can we tell if its electromagnetism that drives magnets apart or some other hidden law that does it? In this case why would it matter? the laws that describe it still function the same way everytime. It seems redundant to add a clause of "part of something that has a working model has some unexplained mechanism that drives it that we cant know about."

[Anonymous No.12630509]

>>12630391
I've never actually had consensual sex, because I associate the act with death as a result of being beaten, choked, raped, and nearly killed when I was around 8 by a female pedophile (whom I was in love with) and her associates. I don't want this to be a dick measuring contest; that won't help anyone. Just realize your perceptions of others are inaccurate, everyone experiences unfair hardships in life, and it's ultimately our own responsibilities to overcome them.

[Anonymous No.12630529]

>>12630509
seek professional help anon, people go to university to help people with these things. Complaining on an internet forum to math autists wont help anybody.

[Anonymous No.12630544]

>>12630470
I guess you're right. I was more just trying to clear up my confusion about the significance of non-local hidden variables. But yes your points are all good.

>It seems redundant to add a clause of "part of something that has a working model has some unexplained mechanism that drives it that we cant know about.
Exactly, which is why I'm confused about non-local hidden variables. It makes more sense to just say that there's a law that governs particle behaviour and that this law incorporates certain variables, than to posit the existence of "hidden" variables.

But yeah I need to do more reading on this.

[Anonymous No.12630545]

>>12630509
did she peg you? if not, no you weren't """"raped"""".

[Anonymous No.12630562]

What's a good website to use to get step by step retard-friendly answers for calculus problems?
I don't mind paying a couple dollars per month.
I was using symbolab and I'm curious if there's anything better out there.

[Anonymous No.12630577]

>>12630529
Tell it to the guy I was responding to my point was just that his assumptions about others are incorrect

[Anonymous No.12631029]

>>12628661
No. Stoichiometry, percent yield, mole fractions, pH calculations, gas laws were fairly straight forwards in Chem I. Only thing I had to know by heart was pv=nRt.
Now there's roughly 5 different ways to calculate heat of a system, enthalpy of formation, etc. And this is only week 2 of the semester.

[Anonymous No.12631081]

is there something like OSSU but for math?

[Anonymous No.12631270]

I'm trying to find a straightforward and simple resource for understanding magnetism/electromagnetism and (this should be telling if my awareness on this field) what the difference is between the two.

Pls no bully.

[Anonymous No.12631291]

>>12631270
Theyre the same thing.
https://www.feynmanlectures.caltech.edu/
Though it would help you to first get a proper background in calculus and linear algebra, if you dont already, to be able to understand whats going on.

[Anonymous No.12631317]

>>12630509
>because I associate the act with death as a result of being beaten, choked, raped, and nearly killed when I was around 8 by a female pedophile (whom I was in love with)
Yeah, that's a therapy question, anon. I'm in a somewhat similar boat where I grew up believing that anyone I get emotionally or physically close to will leave, which left me quite emotionally stunted. While that story is yours, and revealing it to others gets them to give you the understanding that allows you to function socially, it doesn't need to be what defines you. Therapists can help you face this, but it ultimately comes down to you being the one that must overcome it (and yes, that's wholly unfair, that's life).

From personal experience, the perk of this brutal violation of your entire being is that you will have constructed absolutely impenetrable defensive walls between yourself and others because of this. When you challenge your own demons you approach wholeness. When you approach wholeness, you then learn that your defensive walls don't have to be unconscious all-or-nothing ultimatums. They can become tools for your own continued growth.

My way of viewing this paradigm is that you can spite your abusers by turning what they did to you into the ladder rung that allows you to reach higher than they ever could.

Good luck.

[Anonymous No.12631360]

>>12631291
>>12631291
This is most excellent, thank you anon.

[Anonymous No.12632341]

>>12629814
Light heats matter up when it is absorbed by that matter. For the incident light to be absorbed, there must be a transition in energy within that matter, which is the same as the energy of the incident photons. Despite the name "quantum", when you get to anything larger than a hydrogen atom, particularly multi-atom molecules such as water, the energy levels become somewhat broad. Solvation and chemical environment can also affect the spectrum. See attached microwave absorption spectrum of water I found online - you can also find the infrared and visible spectra if you look.

>And can the same logic be applied to sound waves through a body?
Maybe? The sound wave is so large though that I imagine it is into the realm of classical mechanics. Can you heat something up by shouting at it for a long time, or pointing a speaker at it? Probably, if you tried really hard, you could heat it up. Sort of like blowing on tea to cool it down. I doubt you would get much warmer than room temperature though, I think the rate at which you put energy into the body would be much lower than something like a microwave or lightbulb would.

[Anonymous No.12632491]

How practical/hands on is the telecommunications area of an EE degree? I'm a current EE student and need to choose which specialty to study in my last year. I was considering teleco over mechatronics because I dislike working with PCBs/soldering. How deluded of me is it to think teleco will involve little PCB design and be mostly theoretical work? Thx!

[Anonymous No.12632551]

Is Differential Equations harder than Calculus 2 and Calculus 3? My college made Calculus 2 and Calculus 3 intentionally harder than usual and it kind of traumatized me more than I would like to admit. I studied my ass off to pass the calculus curriculum and I don't know how differential equations compare to the two in terms of difficulty.

[Anonymous No.12632572]

Can someone explain potential energy to me in a way a retard could understand?
I have a ball on top of a cliff. The cliff is 10 units high. Thus the ball has 10 units of potential energy that is converted to kinetic energy when I push the ball off the cliff.
But if I were to dig a little bit of the earth up, the distance between the top of the cliff and the bottom of the cliff is now 11 units. The ball didn't do anything, I just moved some shit around.
Additionally, I could load the ball unto a cannon and fire it somewhere. I can do anything with this ball. Doesn't this mean the ball has infinite potential energy? And every particle in the universe has infinite potential energy? Does it just exist as a concept to explain events that have already occurred? Why do we have it?

[Anonymous No.12632606]

>>12632572
potential energy is always relative to something. when you say the ball has "10 units of [gravitational] potential energy" you are implicitly saying that this is relative to the gravitational energy on the surface of the earth (which is taken to be 0).
if you dig a hole 1 meter down, your ball still has "10 units of potential energy" relative to the INITIAL height of the earth. it has 11 units relative to your new hole location. your ball ALWAYS had 11 units of potential energy relative to the new surface, but you weren't considering that because it was covered up with dirt. it's not often very useful to say "I have 15 kJ of gravitational energy relative to 30 cm underground." your ball has a gravitational potential energy relative to every other object, including the moon, the sun, etc..

it seems your biggest source of confusion is thinking that "gravitational potential energy" is intrinsic, when it is in fact extrinsic. saying the ball "has" potential energy is probably confusing you for this reason.

the reason we have it is because of energy conservation. if you want to fire your ball from a cannon to a height where it has 100 units of gravitational potential energy, you must have at least 100 units of energy put into the ball by firing it. when you raise the ball 10 units high, you must put at least 10 units of work into raising it to this height.

[Anonymous No.12633276]

>applying to uni summer research programs
>application asks what race i am
>says its optional
>am white
any argument for leaving it blank?

[Anonymous No.12633314]

>>12633276
saying you're white and leaving it blank are basically the same answer. I'd answer it so you don't look like an autist

[Anonymous No.12633344]

>>12632551
Depends on your syllabus and teacher much more than the subject as such. Typically it's maybe a little bit harder, but your school sounds unusual. What book are you using?

[Anonymous No.12633366]

>>12628247
If you like terse books Wasserman's All of Stats is good for prob/stats. The standard reference is Cassella and Berger, but I dont know it.

Tsitsiklis has a great MIT OCW class with lectures and lectures for probability. He also has a text w Bertsekas, which I've heard good things about. For more intermediate probability, Grimmett's Probability and Random Processes is fucking great, but it's probably better for a second pass

For LA, I can warmly recommend the Strang text (more like course notes than a textbook) and OCW lectures as well for a normal class. Axler's book is good for more theoretically oriented courses.

If you're rusty on calculus, it's not a bad idea to do a quick review of the essentials: differentiating, integration techniques, setting bounds on double/triple integrals, etc.

[Anonymous No.12633367]

>>12626397
You don't need it. All of the math charts are fucking nonsensical and made by people who manifestly don't know math

[Anonymous No.12633379]

>>12624641
>>12624577
The charts are both memes, as is spivak. Don't use spivak for intro calculus. If you want a more rigorous grounding, just learn analysis after. Spivak is only good for people who took high school calc and want more without analysis. The theory from spivak won't be enough for a PhD anyways – you'll need analysis. It'll just unnecessarily slow you down as you learn the basics.

If you're okay with lectures, the best way to learn calculus on your own really is, as others have said, to take the MIT OCW lectures. Do the homework and exams. Check your answers. This is will be quicker and better than working through a text on your own, because you have someone who knows more than you emphasizing the important parts. If you're, for some reason, dead set on a textbook, then yeah Apostol is good.

>>12624681
demented

[Anonymous No.12633515]

>>12628247
https://4chan-science.fandom.com/wiki/Mathematics#Linear_Algebra
https://4chan-science.fandom.com/wiki/Mathematics#Ordinary_Differential_Equations
https://4chan-science.fandom.com/wiki/Mathematics#Probability_and_Randomness

[El Arcón No.12633548]

>wanting it to be easy
Why did pic related get invented, do you think?

[El Arcón No.12633563]

>>12633548

[Anonymous No.12633595]

I need to know the neoclassical growth model for work and I don't know calculus (I assume calculus explains the following). How does the fraction decompose into a subtraction?

Rate of change of capital per worker

Δk/k=ΔK/K-ΔL/L
where k=K/L

[Anonymous No.12633646]

>>12633367
We need a chart that has a normal curriculum then?

[Anonymous No.12633707]

I like foreign languages, language itself and translating. Would I be homeless doing a BA in Translation Studies? Can I move into academia?

[Anonymous No.12633725]

Hey guys I think I might actually get hysteria/conversion disorder/FND not joking this time.

Whenever I imagine making love to the girl down the street who I seriously need to talk to and ask out
I see images of my dad
first it was him smooching, now it progressed this second time this night to him licking the plate like a savage

this hurts and is very painful emotionally, i got up at 3 am for this fucking shit. about to finish case studies in hysteria. parents being assholes has been a thing for a while now and is quite distressing.

and then I heard/dissociated my actual unfeesible crush talking to me in my mind 'don't i get any...?' and whatnot

the things i imagine him doing i imagined doing first! fuck!!? WARbGARBL!?

so far, i had SZA in life. i think that's going away or being managed. now I'm dissociating and noticed all these personalities in my head that have always been here. also was transgender for awhile because of a flashback involving my dad.

shall i bring it up with my therapist? get a new therapist? any comments?

[Anonymous No.12633727]

>>12633725
one more thing, i have a movement disorder already any that's been pointed out futilely by me before

[Anonymous No.12634106]

I have to learn some shell scripting to make a windows machine communicate with unix and android.
I'm already fluent in python (and knowledgable in computer science theory, for what it's worth.)

Anybody good a good overview or tutorial, be it in text, tasks or video format?
Thank you.

[Anonymous No.12634114]

>>12633725
>>12633727
I had to beat the fuck out of my dad to solve this. I had to beat him into submission. You have to hurt him, violently.

Psychiatrists and life coaches have helped me before, but they were huge men that wanted to kick my dads ass. You have to fuck him right up.

[Anonymous No.12634396]

is there any reaction with 0 enthalpy?

[Anonymous No.12634551]

>>12620433
You're correct.
They're just being abusive to the notation.

[Anonymous No.12634556]

>>12627274
Think of a plane represented by two vectors in R^2, if you project that plane into R^3 you don't gain a dimension on the plane you just have a plane.

[Anonymous No.12634565]

>>12620433
[math]\dfrac{\sqrt{(dx)^2 + (dy)^2}}{dt} = \dfrac{\sqrt{(dx)^2 + (dy)^2}}{\sqrt{(dt)^2}} = \sqrt{\dfrac{(dx)^2 + (dy)^2}{(dt)^2}} = \sqrt{ \left( \dfrac{dx}{dt} \right)^2 + \left( \dfrac{dy}{dt} \right)^2}[/math]

[Anonymous No.12634575]

>>12633548
>Why
A need is often a good start for inventions.

[Anonymous No.12634823]

For bra-ket notation does a|i>=|i>a when a is a scalar?

[Anonymous No.12634830]

I have a much better grasp on diffy queues now than when I was taking my first ODEs class. However, I'm still not clear on one thing. I'm an engiqueer so sorry if I butcher terminology. Here's what I want to know: it possible for two (or more) types/families of functions (that are *not* just some clever transformation of eachother) to satisfy the same differential equation?

I can't narrow down an answer for myself. On the one hand, differential equations describe a function via a set of restrictions that "subtractively" (in the musical subtractive synthesis way) narrow down what possible forms that function can take. You're going from general to specific. So it seems to me that it could be possible for two disparate families of functions to satisfy the same restrictions.

But (and I think this is a much more convincing argument), loosely speaking, the *entirety* of a function is contained within its derivatives; that is, you can reconstruct a function solely from its derivatives.
"If two functions have the same derivative, then the functions are the same, separated by a scalar constant". With that damning fact, it seems it would also hold for an equation containing multiple derivatives of the function, a differential equation.
If we allow two disparate families of functions to satisfy the differential equation, they would necessarily require the same derivatives, and I think I've reached a contradiction.

So, what is the case?

[Anonymous No.12634840]

>>12634830
Idk what do you mean for different families of functions. But if I have understood you correctly yes, of course you can have that case.

Take for example the ODE:

[eqn]t^3y'''-2ty'+4y=0[/eqn]

Check that [math]1/t, t^2[/math] and [math]t^2log(t)[/math] are solutions of the ODE.

[Anonymous No.12634843]

>>12634823
Yes.

[Anonymous No.12634915]

is there any special importance or meaning to parametric equations whose equations are successive derivatives of a function?
like, (x=f(t), y=f'(t), z=f''(t)...)

[Anonymous No.12634917]

Where would be the best place to post a statistical studies or projects I make?
I want to do studies on various data I find interesting and write official reports, but it's not for school or anything.
Would a site like Medium work or should I use something else?

[Anonymous No.12634919]

>>12634917
unironically tumblr, just use it as a blog hosting platform instead of a social media platform

[Anonymous No.12635735]

Anyone use gurobi on python? Trying to figure out why my code (https://pastebin.com/PB7FFNQ6)) is giving me the error: gurobipy.gurobipy.GurobiError: Unable to convert argument to an expression

[Anonymous No.12635767]

Hey gurus, there is a "trick" question, where we have to calculate the principal components of a matrix where the covariance matrix is the identity matrix. What does that mean intuition-wise? The matrix is already made up of independent features and therefore the matrix itself is the matrix of principal components?

$(Cov(\mathbf{X}) = \begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}$

[Anonymous No.12635784]

>>12635735
>list comprehension with parenthesis
I don't recall Python working like that.

[Anonymous No.12635788]

>>12635767

[math]Cov(\mathbf{X}) = \begin{pmatrix}
1 & 0\\
0 & 1
\end{pmatrix}[/math]

[Anonymous No.12635939]

>>12635784
that's what some guy on stack exchange gave me, but it doesn't seem to work. My guess is that whatever the "list comprehension with parenthesis" is doing isnt creating a valid expression. Though Im notsure what it should be

[Anonymous No.12635968]

A long-shot, but has anybody here studied at the Ecole Polytechnique de Laussane? I'm considering doing a Master's in Communication Systems (I'm finishing my bachelor's in EE this year) there next year, and would like to know the experience of anybody that has studied there.

[Anonymous No.12635981]

>>12618423
> Measuring complexity of theorem
Probably by number of operations you need for shortest proof to the theorem, broken down to elementary operations.
> Infinitely many ways to proof a theorem
There probably is. Most open problems in geometry were solved by calculous and complex analysis. New tools are being developed everyday, giving every problems infinite ways to be proven.

[Anonymous No.12635990]

Is there any sort of physics engine that let's you enter the knowns and unknowns and solves problems?

coming from the perspective of someone struggling with a physcs textbook in front of me. it would be great to just type in what I know, type in the "class" of problem it is, type in the desired unknown, then it presents some equivelancies and how I may get there

[Anonymous No.12635999]

>>12619551
Gender non confirming.
Then proceed not to confirm your gender.

[Anonymous No.12636025]

>>12622947
Markov chains work on economic models.
Economic models aren't practical math, but so is markov model.

[Anonymous No.12636040]

>>12636025
>Markov chains work on economic models.
source?

[Anonymous No.12636089]

>>12635939
https://www.w3schools.com/python/python_lists_comprehension.asp
This is list comprehension. Note the square brackets.
The code in your page seems to do list comprehension with parenthesis instead at (gb.quicksum(gb.quicksum(cost[i,j]*gb.quicksum(shipments[k,i,j] for k in grapes)) for j in wineries) for i in vineyards)
This is weird, for me. I don't have access to a computer right now tho, so I can't test if that's actually the issue.

[Anonymous No.12636102]

>>12636089
I think thats okay as they use it here:
https://www.gurobi.com/documentation/9.1/quickstart_windows/cs_netflow_py_example.html

[Anonymous No.12636192]

given that we're on the topic of markets and economics, why does the index 500 growth always exceed that of inflation? is this just "the rich get richer" taking place?

also, is there non-gov't investing that isn't gambling? like index funds seem to do good. dont' tell me to buy BTC, I've been buying since 2014. asking because I've got a lot of friends who seem to into investing as they get older, despite not having the amount of cash to justify worrying about such a thing. I've been of the mind that developing income producing assets squashes buying low and selling high, though it interest that so many opt for the ladder.

[Anonymous No.12636421]

What's more rewarding to self-study? Mathematics or physics?

[Anonymous No.12636442]

>>12636421
mathematics for sure, physics is just applied math at a certain point anyway

[Anonymous No.12636449]

>>12635784
>list comprehension with parenthesis
That's a generator expression. Lists and generators are both iterables, i.e. you can use for...in on them.

[Anonymous No.12636450]

>>12636442
I'm just torn because I feel like a lot of mathematics is just made up, if you study the foundations it has trouble justifying it. When I study physics it feels like they are just making shit up as well (dark energy, whatever). I just want something that's comfy and isn't pointless.

[Anonymous No.12636502]

Why does this one LED bulb keeps faintly shining after I turn it off?

[Anonymous No.12636517]

>>12636502
Capacitive leakage in the switch wire + no discharge resistor across the output of the bridge rectifier.

[Anonymous No.12636540]

>>12636502
>>12636517
https://www.youtube.com/watch?v=_bgUy6zA0ts
https://www.youtube.com/watch?v=tzWz_guJHvY

[Anonymous No.12636594]

>>12618121
Any optimal control chad around? I'm working on a fedbatch biorreactor for a cell culture. The system dynamics is a 20 something state variable ODE system with 2 different inputs, where some parameters like the cell growth rate are functions defined by part, and the control input can only work every 8 hours (lab wagie 1 and 2 can only inject shit every 8 hours).

I have two questions, has anyone worked on something similar on matlab and/or python and what toolbox did you use? The thing is that making a PID controller for it was easy as shit but I can't wrap my head around this shit. Seems like most toolboxes are for easy problems that will converge on the shittiest solvers. I guess acado or amigo2 are the only ones I haven't tried.
And the other is the shit that is driving me nuts, how would you even begin to implement that the wagie can only work when he gets to his job and just before leaving thing? Basically the system is simulated for all times but the optimal control policy is calculated taking into account that it only works at 8 am and 4pm every day. I mean, I guess I could make a constraint making it so it's 0 at some time intervals, but found some guy that said it fucks with the smoothness of the solution and my thesis professor said it wasn't that trivial to implement. Maybe he was just fucking with me that faggot. Fuck this shit method.

[Anonymous No.12636710]

how early do you need to ask for a rec letter? i need one by the 12th and im worried that its a bit late and the prof will be annoyed or whatever.
also, if i need rec letters for a bunch of different applications, can i ask the same prof for all of them? do they just copy/paste the thing? whats an appropriate number of different applications before it looks unprofessional? im up to 5 rn

[Anonymous No.12637647]

>>12636450
The higher levels of any intensive field of study is very abstract. If you want justifiable physics stick to the deterministic models, based on classical mechanics. This will get you as far as General Relativity but the math chops you need for this is quite involved too. If you decide to study physics youll study math at the same time.

[Anonymous No.12637668]

I have a circuit diagram.
My answer has negative amps.
Is this possible?

[Anonymous No.12637691]

>>12637668
it just means the flow of current is the opposite of the one on your diagram

[Anonymous No.12637695]

>>12637668
Yes, the amps is flowing in the opposide direction. If youre worried reverse your initial assumption of the direction of the current and do the same analysis.

[Anonymous No.12637696]

>>12637691
Thanks.

[Anonymous No.12637845]

>>12635767
[math]\det(A-\lambda I)=\det
\begin{bmatrix}
1-\lambda & 0 \\
0 & 1-\lambda \\
\end{bmatrix}=
0 [/math]
[math](1-\lambda)^2=0 [/math]
One repeated solution [math]\lambda=1 [/math]. For such solution
[math](A-\lambda I)v=0 [/math]

[math]
\begin{bmatrix}
1-\lambda & 0 \\
0 & 1-\lambda \\
\end{bmatrix}
\begin{bmatrix}
v_1 \\
v_2 \\
\end{bmatrix}=
\begin{bmatrix}
0 & 0 \\
0 & 0 \\
\end{bmatrix}
\begin{bmatrix}
v_1 \\
v_2 \\
\end{bmatrix}
=0
[/math]
The eigenvectors are arbitrary. The eigendecomposition for PCA will just depend on the choice of an orthonormal basis of [math]\mathbb{R}^2[/math] as the matrix of the eigenvectors.

[Anonymous No.12637923]

new thread
>>>12637888

[Anonymous No.12638018]

>>12637923
>making a new thread before bump limit
Putting the s in /sqt/ I see