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/sci/ - Science & Math

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12128061 No.12128061 [Reply] [Original] [archived.moe]

Molecular spectroscopy edition
>what is /sqt/ for
Questions regarding math and science, plus appropriate advice requests.
>where do I go for other SFW questions and requests?
>>>/wsr/ , >>>/g/sqt , >>>/diy/sqt , >>>/adv/ , etc.
libgen.is (link might break)
>journal articles?
sci-hub (you'll have to google for a link, unfortunately)
>book recs?
>how do I post math symbols?
https://i.imgur.com/vPAp2YD.png (and see first reply)
>how do I successfully post math symbols?
>a google search didn't return anything, is there anything else I should try before asking the question here?
>where do I look up if the question has already been asked on /sci/?
>how do I optimize an image losslessly?

Question asking tips and tricks:
>attach an image
>make sure relevant variables are clearly defined
>if a question has two or three replies, people usually assume it's already been answered
>ask anonymously
>check the Latex with the Tex button on the posting box
>if someone replies to your question with a shitpost, ignore it

Meme charts: https://imgur.com/a/kAiPAJx
Serious charts: https://imgur.com/a/Bumj2FW (Post any that I've missed.)
Verbitsky: https://imgur.com/a/QgEw4XN
Graphing: https://www.desmos.com/
Calc solver: https://www.wolframalpha.com/
Tables, properties, material selection:

>> No.12128104
File: 364 KB, 780x4182, 1600202762696.png [View same] [iqdb] [saucenao] [google] [report]

last thread: >>12108436

unanswered questions and their fields:
>>12122742 || anatomy
>>12125006 || anatomy
>>12125091 || anatomy
>>12111359 || anatomy/biology
>>12108565 || biology
>>12113957 || biochemistry
>>12119726 || chemistry
>>12116906 || earth science
>>12117094 || electronics
>>12108614 || math
>>12121624 || math
>>12115337 || mathematical physics
>>12113648 || physics
>>12128044 || physics
>>12127322 || misc.

>> No.12128125

your understanding of LEDs is pretty poor. the two different types of semiconductors, n and p types, have either an abundance or a lack of electrons (respectively). flowing a current through this causes electrons at the junction from the n-type to recombine with the p-type holes.
these two are at different energy levels corresponding to the band gap, so when the electron drops in energy it emits light corresponding to that energy.

>> No.12128174
File: 70 KB, 726x179, Screenshot 2020-09-16 132731.png [View same] [iqdb] [saucenao] [google] [report]

Can someone explain to me why elastic potential energy at (a) would be 0 while elastic potential energy at (b) would be max? I thought that at (a) it would be the highest potential energy and at (b) it would have the lowest elastic potential energy because it's also where the kinetic energy is at the highest.

>> No.12128242

if you take an infinitesimal element of the string, the elastic potential will be greatest when it's being stretched the most (U=kx^2). so, we have to figure out where this maximum stretch is.
since your string is not stretching at all in the x direction, any stretch has to be vertical. at the peaks of the wave, the point at the peak has no vertical stretch (slope=0). the slope at y=0 is the largest, and you can see the string is stretched the most vertically there.

you're probably thinking of gravitational potential energy, which would be the highest at a since the segment of the string is the highest. either that, or you're thinking of the string as a spring with equilibrium position y=0 and maximum/minimum at ym. this is not correct, you need to think of the string as one long spring and pick the point where that spring would be stretched the most.

>> No.12128254

question unclear. Is there a semi-permeable membrane involved? When you say 10:1, what exactly is the 10? K+, or KCl?
Is a neutral counterion like NO3- present?

>> No.12128258

highest displacement -> highest potential energy
Also v=0 at (a), so E_kin=0

>> No.12128291

>you're probably thinking of gravitational potential energy, which would be the highest at a since the segment of the string is the highest.
Yea I was thinking of it that way which really did confuse me.
>any stretch has to be vertical. at the peaks of the wave, the point at the peak has no vertical stretch (slope=0). the slope at y=0 is the largest, and you can see the string is stretched the most vertically there.
Okay yeah, I think I'm getting what you mean now. At slope = 0, the string is 'back to normal' and at the highest slope, the string is the most stretched so it has the most 'tension stretch'(like a rubberband I guess?) which builds up a lot of potential energy waiting to be released... right?
>highest displacement -> highest potential energy
Got it, highest displacement in terms of amplitude (ym).

Thank you both so much!

>> No.12128335

im thinking of picking up smoking, what brand do you guys rec (burgerstan)

>> No.12128339

I recommend you talk to my grandmother who is currently on a manual breathing machine in the ICU due to COPD from smoking for just 10 years when she was younger.

>> No.12128342

whats her number

>> No.12128343
File: 10 KB, 223x226, download (2).jpg [View same] [iqdb] [saucenao] [google] [report]

Marlboro reds.

>> No.12128347

>Smoking bad
Absolute reddit take.

>> No.12128348

Go ahead and smoke, if you're that retarded to pick it up then you deserve the abysmal death that almost every smoker experiences

>> No.12128352

>10 years
i only got 2 more years of undergrad + 7 years for phd so im in the clear

>> No.12128363

There is nothing wrong with smoking, though.

>> No.12128385
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>> No.12128389
File: 247 KB, 863x515, how do we know what the lower electriacl potential is.png [View same] [iqdb] [saucenao] [google] [report]

How do we know what the lower electrical potential of the circuit based on the diagram 2.10? Or is there a formula for it?

>> No.12128454

Not an argument. Smoking is linked to many positive health benefits.

>> No.12128559
File: 843 KB, 1200x1200, __kaku_seiga_touhou_drawn_by_sokura_mochichitose__081060d6de4b368ff8fca0a552a8b06c.jpg [View same] [iqdb] [saucenao] [google] [report]

Nice job lad.
By the by, warosu added >> to its own link when you got the pasta from the archive.
Also, you can link to sci-hub.tw now.
And feel free to modify it more, it wasn't written so it would stay the same forever.

>> No.12128644

yeah next time I'll put more work into tweaking it. there's a lot of info, I might condense it a bit

>> No.12128651
File: 26 KB, 385x178, inequality.png [View same] [iqdb] [saucenao] [google] [report]

How to use the Cauchy schwarz inequality to prove pic? I've been messing this one up for a while and think i'm just not seeing the obvious.

>> No.12128689
File: 463 KB, 1242x1501, 1577773021593.jpg [View same] [iqdb] [saucenao] [google] [report]

[math]\left(\sum_{j=1}^n|x_jy_j|\right)^2 \leq \sum_{j=1}^n|x_j|^2 \sum_{j=1}^n|y_j|^2[/math]

So assuming you are dealing with positive real numbers [math]a_j,b_j[/math]
Let [eqn]x_j = \frac{a_j}{\sqrt{b_j}}, \quad \text{ and } \quad y_j = \sqrt{b_j}[/eqn]
Then you easily obtain
[eqn]\left(\sum_{j=1}^n \left|\frac{a_j}{\sqrt{b_j}}\sqrt{b_j}\right|\right)^2 \ \leq \left(\sum_{j=1}^n\left|\frac{a_j}{\sqrt{b_j}}\right|^2\right)\left(\sum_{j=1}^n\sqrt{b_j}^2\right)[/eqn]

From here your equation follows easily.

>> No.12128694

a cube has a diagonal of length 2
what is the side length of the cube?
Exactly, no decimals

>> No.12128704

[math] \frac{2}{\sqrt{3}} [/math]

>> No.12128740

Isn't this just plugging in something to fit? I felt like I was supposed to derive that one in the picture from cauchy-schwarz. Driving me crazy.

>> No.12128745
File: 23 KB, 458x336, AnsoffMatrix.jpg [View same] [iqdb] [saucenao] [google] [report]

Is there a specific name for this type of diagram or categorization? I.e. 2 pairs of categories resulting in a category for every combination of those.

>> No.12128759

decision matrix

>> No.12128788

Nah, that's too specific

>> No.12128795
File: 61 KB, 1300x866, 40800869-2d-cartoon-image-of-table.jpg [View same] [iqdb] [saucenao] [google] [report]

then it's just a type of table
pic related when you google 2D table

>> No.12128796
File: 1.71 MB, 3472x3433, IMG_20200916_135149_1.jpg [View same] [iqdb] [saucenao] [google] [report]

I know the limits of h and the lower limit of t but I can't figure out how to set up the integral because Im dumb
pls halp

>> No.12128802

it would be helpful if you described what the problem was so we didn't have to read your mind

>> No.12128825

What are we even looking at?

>> No.12128833

Like, I can read the thing.
I literally just don't know what it is you want to do.
Water falls in big circle and leaves through small circle.

>> No.12128907

Is Linguistics a good major to double major with Applied Mathematics ?

>> No.12128914

do you like linguistics? if yes, then do it.
nothing makes a "good" major besides what you want to major in and what you want to do with your life.

>> No.12128921

This but unironically.

>> No.12128925


But are they synergistic? I'm looking at it from a perspective of developing human-accurate speech synthesis.

>> No.12128931

my post was unironic
if you want to do anything that involves both fields then sure. most likely your major will be 1% of your knowledge going into the field, and the remaining 99% you'll learn doing the work and learning the specifics to your field.

>> No.12128934

I majored in math and minored in Korean, for what it's worth.

>> No.12128948

How does subtracting the starting point to the end point on a graph finds its change? I can't visualize it in my head when negative numbers are involve. Help

>> No.12128955

some stuff flows into a tank at 32kg/s, density 2500kgm-3
cross sectional area of tank has radius r1
cross section of exit pipe has radius r2
the speed it leaves is sqrt(2gh)
so volume flow in = 32/2500
mass out = sqrt(2gh)*(pi*r2^2)
This problem starts when the height of the fluid is h1 (I know what it is) and I need to found how long it takes to overflow the tank (height of the tank is h2 = h1 + 2)

>> No.12128960

the change of a graph is the difference of the y-values from start to finish.
it's like with anything else, subtraction finds the change. if you want to lose weight, and you weigh 500 pounds and then you go to 250 pounds, your weight change is 250-500=-250 pounds.
say your house is at x=0. if you walk to the right, you walk in the "positive" x direction, and to the left is the "negative" x direction. say you start at 5 meters to the left of your house and then walk to 5 meters to the right. how far did you walk? 5-(-5)=10 meters

>> No.12128965 [DELETED] 

You know how much volume accumulates per second into the tank and you know the tank's volume, what are you messing with the height for?

>> No.12128973

Let [math]k \in \mathbb{N}, 0 \le c_1 < ... < c_k \le 1 [/math]
[math]a, b \in \mathbb{R}, a < b[/math]
[math]b_1, ... , b_k \in \mathbb{R}[/math]
For [math]f: [a,b] \to \mathbb{R} [/math] and [math]h = b - a[/math] the quadrature rule Q is given as
[math]Q(f) = h\sum_{n=1}^{k} b_jf(a + c_jh)[/math]
If f is integrable define the error R(f) of f as
[math]R(f) = \int\limits_{a}^{b} f dx - Q(f)[/math]

Show, if [math]m \in \mathbb{N}, m \ge k - 1[/math] and Q is exact all polynomials with degree at most m
(meaning for all polynomials q with deg(q) [math]\le m[/math] it holds that [math]R(q) = 0[/math]
[math]\exists c \in \mathbb{R}^{+}[/math] such that [math]\forall f \in C^{m+1}([a,b])[/math] it holds that
[eqn]\vert R(f)\vert \le ch^{m+2}\|f^{(m+1)}\|_{\infty}[/eqn]
with c being independent of the interval [a,b].

Hint: Expand [math]0 \le c_1 < ... < c_k \le 1 [/math] to [math]0 \le c_1 < ... < c_{m+1} \le 1 [/math] and interpolate f with a polynom q of degree m at [math]a+c_1h < ... < a+c_{m+1}h \le 1 [/math]

>> No.12128978
File: 84 KB, 952x487, fknwut.png [View same] [iqdb] [saucenao] [google] [report]

I have no idea what to do here. I'm feeling ultra dumb.

>> No.12129026
File: 213 KB, 600x658, __remilia_scarlet_and_flandre_scarlet_touhou_drawn_by_arnest__f472c1e784c502b9ef9f41eb730dea00.png [View same] [iqdb] [saucenao] [google] [report]

[math]a_1 = 1, a_2 = 4, a_3 = 9, b_1= a+b, b_2 = c, b_3 = a+b+c [/math]

>> No.12129028

kill me now. ty

>> No.12129030


>> No.12129036

>kill me now
No, no, this is some real schizo wild guessing shit, there's really no shame in getting stuck.

>> No.12129050

Well, I just realized that it's even easier. Take the LHS, and just plug into RHS of the other inequality. Like a_1 =1, a_2=16, a_3=81., b_1=a+b, b_2=c, b_3=a+b+c.

However, still not sure about >>12128651
The other anon was kind enough to answer, but it just feels ad hoc.

>> No.12129067

Given a random variable X and a borel function f such that fX is not a.s. constant, is it possible that X and fX are independent? I'm pretty sure that it is no.

>> No.12129084

I'm confused. So say I'm "*" and "0" is my house, I start 5 meters to the left of my house

* - - - - 0 + + + + +

Then I walk 5 meters to the right
- * - - - 0 + + + + + (Step 1)
- - * - - 0 + + + + + (Step 2)
- - - * - 0 + + + + + (Step 3)
- - - - * 0 + + + + + (Step 4)
- - - - - * + + + + + (Step 5)
Isn't it 5 meters I walked?

>> No.12129094

And by even easier I just mean the same thing. Oy.

>> No.12129103

if you start 5 meters above water, and you dive to 5 meters below the surface of the water, how many meters down did you go?

what is your notation, do you have no math experience whatsoever?

>> No.12129120

It's obviously false, but my complete lack of skills at manipulating probability theoretic definitions makes it hard to prove.
There was a definition like "random variables [math]X[/math] and [math]Y[/math] are independent if and only if for any two measurable sets [math]A, B \subset \mathbb{R}[/math], [math]P[ X^{-1}(A) \cap Y^{-1}(B)] = P[X^{-1}(A)]P[Y^{-1}(B)][/math]", wasn't there? It's pretty easy to prove it from that.

>> No.12129134

That’s not really answering the question. You can’t recombine ad Infinitum. My question was how are LED able to continuously do this.

>> No.12129139

yes, you can. because the electrons that go from the n to p type semiconductors are then drawn out into the circuit to form the current.
for any electron that goes from n->p semiconductors, a new one is popped out of the p-type and flows into the wire of the circuit.

>> No.12129149

How would you calc this without trig / a computer?

>> No.12129156

I used my brain
for a square (since it's simpler than a cube to visualize) you have four sides. the diagonal is the line connecting any two opposite corners. so, you imagine a triangle formed by the two sides of the square with the diagonal as the hypoteneuse, and you calculate the side length from there

for a cube it's the same problem, but there are three side lengths that you need (since it's 3D). if you have trouble seeing this, use a physical 3D cube and imagine what the sides of the diagonal would be.

>> No.12129161

Just define it to be ground or 0 volts.

>> No.12129198

Did you consider that the diagonal of a cube is the diagonal of a rectangle with different a and b, where a is the side length of the cube and b is the hypotenuse of the squares? I’m just curious the method for tackling, it’s still strange to me that the diagonal of a unit square is sqrt2 but for a cube is sqrt3

>> No.12129207

>say you start at 5 meters to the left of your house and then walk to 5 meters to the right.
Ohh, so it meant I start 5 meters to the left of my house and walk 5 meters to the right from my house? I thought it meant I start 5 meters to the left of my house and then walk 5 meters to the right from 5 meters to the left.

I only know pretty basic algebra and im kinda retarded

>> No.12129210

no matter how you do it you'll get the same answer
look up how to calculate distances in 3D

>> No.12129217

yes, that's what I meant
you need to work on familiarity with negative numbers. do these problems:

>I started at x=-100 meters and ran to x=-80 meters, how many meters did I run?
>It was cold today but warm yesterday! Yesterday it was 50 degrees but today it was -100 degrees. What was the change in temperature between the two days?

>> No.12129227

Okay thank you

>> No.12129307


The length of the diagonal for a cube of length [math]l[/math] is given by [math]\sqrt{l^2 + l^2 + l^2} = \sqrt{3l^2} = \sqrt{3}l[/math]. If you set this expression equal to [math]2[/math], you can solve for the length.

>> No.12129316

>for a cube of length [math]l[/math]

*of SIDE length [math]l[/math]

>> No.12129407

What should I read if I want to know what there was before everything? I cannot wrap my head around how the universe has started, and the answer "it has always existed" doesn't make intuitive sense to me.
So any books or other resources? Btw I'm an almost graduate physics student

>> No.12129410

if you're almost a graduate physicist you should know that this question is metaphysics. nothing in physics currently addresses this. there's not an answer

>> No.12129445

What about stuff like this?

>> No.12129455

stephen hawkings was notorious for making claims outside of his area of expertise
also, prove it. perform any sort of experiment that provides evidence for this. unfortunately, you can't

>> No.12129503

So whose area of expertise is it? Who would be a physicist more qualified that has written something about it?

>perform any sort of experiment that provides evidence for this. unfortunately, you can't
When you can't make experiments you can still formulate theories. There must be some book or some other resource that gathers and explains the theories that have been proposed up until now

>> No.12129515

nobody, because everyone's ideas are equally shit
there's literally no way to formulate a pre-big bang theory because we have actually 0 idea about what things were like. we don't even have a starting point.
you might as well go to >>>/x/ and ask what they have to say because it will be just as scientific as hawkings theory

>> No.12129538
File: 163 KB, 800x566, 1599214944974.jpg [View same] [iqdb] [saucenao] [google] [report]

>Never manage to study
>Realize the deadline is close, study with intense concentration
How do I fix this? I could do so much more with my life if I had that drive every day

>> No.12129577

you're probably doing other shit every day
remove the ability to do those things. get rid of your internet access

>> No.12129606

If it is nobody's area of expertise then it is not an area of expertise at all. So your critic of hawking doesn't make sense.

>everyone's ideas are equally shit
Ok, then there must be something where these ideas have been discussed and proven to be shit

>> No.12129984

Why does Lagrangian Mechanics use T - V instead of V - T ?
It seems much more intuitive to me to imagine potential energy being subtracted by kinetic energy, because the potential energy is transferred into kinetic energy.

I merely looked over it, but it seems like the integral and the average should be the same, and both should reflect the total energy of the system.

>> No.12129991

nowhere did I claim it to be anyone's area of expertise. your initial link was about hawking, and I was claiming that he didn't know what he was talking about
>discussed and proven to be shit
you don't get it. no theory makes any sense. we literally cannot know about how things were before the big bang, at the moment. I highly doubt you're "nearing grad school in physics" if you ask these questions.

>> No.12130294

what is an average h index for a professor of physics? one of mine has an h index of 102 which seems high but i dont know what to compare it to. he wrote a textbook that is basically the manual for his subfield though so it might be why

>> No.12130440

Humanity builds a research facility on the Moon. What kind of research could be conducted here?

>> No.12130488

I took an IQ test a few years back and got 130. How fucked am I?

>> No.12130663

Pls respond
>>12115337 # || mathematical physics

>> No.12130689
File: 25 KB, 639x165, Capture.png [View same] [iqdb] [saucenao] [google] [report]

Could someone explain how the y^2 became (-1/y^2), I though we were substituting the x and y components straight into the equation for a separable differential equation. Why has it done this?

>> No.12130717
File: 97 KB, 1440x810, Me seething.jpg [View same] [iqdb] [saucenao] [google] [report]

Nevermind, I get it. Geeez, that's such an awkward way of getting to the dy/dx bit,

>> No.12130856

Is making
>asterisk triangle program
>real time stopwatch program
>website page redesign
>web where you can post edit and filter comment
Doable under 2 hours or am i just a complete retard because i can't finish it on time?

>> No.12130857

arccos() isn't distributive, right?

>> No.12130946

Do you mean linear?

>> No.12130947

Usually I see distributivity phrased as "Binary operation A is distributive over binary operation B". What do you have in mind for the meaning of "Function f() is distributive"? It's true that arccos(x+y) is not in general equal to arccos(x) + arccos(y), if that's what you are asking.

>> No.12130958

it is up to the first order approximation

>> No.12131005

If you refer to something as an "area of expertise" then you imply that there are some experts in it, otherwise it's just bad wording.

>you don't get it. no theory makes any sense
>a random 4chan users tell me that any guess about the beginning of time is utter nonsense, and even trying is silly
>one of the most renown scientist of the last century has at least formulated a theory about it
I hope it's obvious that I wont stop my research here because of what you say. But if you have some source to discredit Hawking's theory, or to discredit in general any attempt at such theories, I may

>> No.12131610
File: 105 KB, 1080x1080, blocks.png [View same] [iqdb] [saucenao] [google] [report]

Is there any simulator for these kinds of things.... I hate these slope problems.... how do I find the weight A neccesary to keep the system in balance !??

this is the best I could do but it isnt good

>> No.12131636
File: 127 KB, 900x900, autist in sqt.jpg [View same] [iqdb] [saucenao] [google] [report]

I'm not sure if this was referring to me, but if it was, I'm listening.

>> No.12131639

Question to ee fags, how do you calculate the sop or karnaugh map for a system with more than 5 inputs with more than 10 bits total? You can't obviously do it by hand, so how do I do this? I'm trying to develop PLC code

>> No.12131698

How do I solve the PDE
gyUx - gxUx = 0

Where gy and gx are partial derivatives of some function g(x, y). I'm trying to solve for a U. I understand how to solve
aUx-bUy=0 where a and b are constants, but not the above question with gx and gy.

>> No.12131705

100 is very high. they must be important in the field.
in physics even the big shots in my field are around 50-75. the highest one I've seen is 150, whch is almost unheard of

>> No.12131712

Any interesting questions I should ask my alumni who works at pretty big companies?

>> No.12131713

depending on your experience and how sophisticated you want it to be. the first two seem much easier but I have never done anything like the latter two.
are you talking with a full-blown GUI?

>> No.12131720

Russel's teapot.
Anyone can come up with something that works. The problem is there's no possible way of knowing which theories are better than the others because there's no proof. The big bang erased any information of a pre-existing universe.

It's like asking which beyond standard model is currently true. We have no idea, we just have a lot of theories that we're currently testing. But at least we're able to test them. Unless you can devise an experiment to test pre-big bang dynamics, then any theory might as well be "there were magic unicorns that rules over everything."

>> No.12131729

here are my go-to questions for people like this
don't ask boring questions that you can look up btw.
>is there anything you wish you knew in my position that you know now?
>what aspect of your career preparation (connections, experience) would you say was most important
idk probably some others but that's a start

>> No.12131734

The web redesign is more of the view/display without the functional, so it's being tricky on the css part.
For the last one it's a web but they didn't really talk about the design so probably they want to focused on the functionality, they asked to use framework and make sure it's secured from xss attack

>> No.12131738

by in balance, do you mean stationary?
it's been a long time since I've done mechanics but I'll give it a shot.

>> No.12131743

yes stationary

>> No.12131762

Rewrite as [math](g_y - g_x)U_x = 0[/math].
The solutions should mostly be constant in terms of x.

>> No.12131772

Ah fuck I mistyped it
What I meant to type was:
gyUx - gxUy = 0

>> No.12131773
File: 21 KB, 581x192, geometry.png [View same] [iqdb] [saucenao] [google] [report]

how do I find h
please don't laugh

>> No.12131782

You just want *some* non-trivial U? Because U=g works.

>> No.12131786

Yes exactly. I even guessed that would be the answer, I just can't figure out the actual working to get to it

>> No.12131795

What I mean is, is how do I work towards the solution U=g without assuming its that in the first place?

>> No.12131800

Meant for>>12131782

>> No.12131812

okay nobody replied yet but I got:
Rtan(30) + Rtan(60) = L for the length of each black line so then the height h would be Lsin(30)
any smart people wanna confirm?

>> No.12131820

I personally solved it with inspection, but if you want a maymay justification, then sure, I can give you one.
Notice that [math]g_y U_x - g_x U_y = \omega (\nabla U, \nabla g) = 0[/math], where [math]\omega[/math] is the usual euclidean symplectic form. Symplectic forms are alternating, so for bidimensional space, any vector field [math]X[/math] solving [math]\omega (X, \nabla g)[/math] has the form [math]X = f(x) \nabla g[/math] for some function [math]f(x)[/math] on the points where [math]g[/math] is non-zero. Taking [math]f(x) = 1[/math] gives our current solution.
You can then try to mess around with properties of conservative vector fields and see if anything else shows up to pass the time.

>> No.12131834

okay two things:
I just did the whole problem without realizing that A is on a string. you really really need to write out your problems better because I'm trying to interpret what you're asking based on your scratch work
frictional force is not equal to [math] \mu N [/math] , this is the MAXIMUM static frictional force that is possible. Since you have no motion, your actual frictional force will just be equal and opposite to the applied forces on your object (gravity) in order to cancel them out.

if you want me to work through the problem I'll need you to actually state what the question is, sorry.

>> No.12131835

Rather than a symplectic form, it might be easier for you to think of the determinant of
g_y & g_x \\
U_y & U_x
See? only zeroes when one is a multiple of the other.

>> No.12131840
File: 48 KB, 284x652, 1597361117975.jpg [View same] [iqdb] [saucenao] [google] [report]

about to take my first electromagnetics exam, thanks for all the help bros

>> No.12131848

I'm only just starting PDEs so a lot of this terminology I'm still learning. I came up with a reasonably decent inspect justification (I think).

However I've taken a screen shot of your proof to slowly take in as I do the course, thank you very much. Which textbooks do you recommend learning PDEs from? I have access to haberman and/or Evans, but can get another simple enough. Evans seems a little beyond me currently.

>> No.12131859

Are there no EEs here?

>> No.12131871

U_x g_y- U_y g_x = \begin{pmatrix}U_x\\U_y\\0\end{pmatrix}\times \begin{pmatrix}g_x\\g_y\\0\end{pmatrix}
So basically you want the cross product to be 0, which means U and g must be orthogonal

>> No.12131882

Honestly, my knowledge of PDEs is a weird hodge podge of Appendices on stuff like elliptic pdes and other random knowledge. I can't really recommend you anything.
Evans is constantly recommended, tho, so you should probably insist on making your way through it.

>> No.12131893

The block B is held in place on the slope by friction and block A

Block A is tied to a unmovable wall with the rope that goes parallel to the slope

If weight of block B is known and the friction coefficients from both sides of it, then whatis the minimal weight of block A that would make the system stable ie... in place
also find the forc in the rope

>> No.12131909

I've read the first chapter of haberman and it's very intuitive, but that's to be expected since its main focus is applied PDEs, I'll probably dig into Evans at some point since I'd like to try my hand at postgrad

>> No.12131914

Anything good I can read about burnout? I'm in a deep pit I can't seem to get out

>> No.12131915

Do you have to use Newtonian mechanics?

>> No.12131920

Go for a walk. A long one. Listen to an audiobook/podcast (whatever you feel like, nothing work/study related).

Always helps me both unwind and recharge. If you're daring, by yourself an ice cream on your walk

>> No.12131935
File: 3.07 MB, 776x5164, 15-36-45-1514290698220.png [View same] [iqdb] [saucenao] [google] [report]

Where should I start if ive just done calc 1-3 and diff eq a few years ago but want to learn more? taking a gap year before grad school and want to build on my math

>> No.12131943

What field?
Anyway, linear/abstract algebra

>> No.12131986

Get Pinter's book.

>> No.12132000

Linear algebra and PDEs

>> No.12132048
File: 145 KB, 602x798, scrap.png [View same] [iqdb] [saucenao] [google] [report]

as always, you should check my work for yourself.

>> No.12132072

These are the worst capital sigmas I've ever seen.

>> No.12132073

How do we know Dedekind's construction of the reals is equivalent to Cantor's construction of the reals?

>> No.12132079

>Dedekind's construction of the reals

>> No.12132080
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my calculator died so i had to do all the calculations by hand

>> No.12132106

Did you do good?

>> No.12132125

chad handman

>> No.12132136
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>> No.12132284

I realized long ago I could never draw them quickly so I settled on something that I could do fast and was still unambiguous

>> No.12132329

How did the dingos do it?

>> No.12132331

Thanks and will do

>> No.12132364
File: 96 KB, 1280x409, 1.jpg [View same] [iqdb] [saucenao] [google] [report]

Brainlet question here
Can anyone explain me the answer? I don't get it

>> No.12132372

>The problem is there's no possible way of knowing which theories are better than the others because there's no proof. The big bang erased any information of a pre-existing universe
this is just an example:
>Did time even exist before the Big Bang? Was there some kind of reverse Universe? Everybody is welcome to their pet theory on how our Universe came to look as it does, but only one can be a winner. To help decide which ones stay and which ones go, the researchers proposed using observable attributes that we can link with discriminating features of inflation-based models.
They literally talk about how to tell which theories are better than the others

>> No.12132401

this is equivalent to saying
>the theories that are better than others are the ones that recover the current universe in the right conditions
nobody is making theories that don't do that. this is a baseline condition for any new theory. even the wackiest string theory models have to recover the observable universe or else they're immediately thrown out.

when I say "no way of knowing what's better than others" I thought it was implied that this meant "out of the valid theories, there's no way to know which is better than others"

>> No.12132442

iirc, "negative y surface" means that the fluid is acting on the surface with a normal pointing in the negative direction, same reasoning goes for the lower plate

>> No.12132620
File: 60 KB, 427x640, 5b320dd7e956b3549aa727e6d4cd196a.jpg [View same] [iqdb] [saucenao] [google] [report]

Is it true that if i sleep standing up,my ears center of balance tricks my brain into having a lucid dream?

>> No.12132814
File: 879 KB, 2847x3708, 0177ad765ba3ddcdfa025452ec20c617c.jpg [View same] [iqdb] [saucenao] [google] [report]

Pen and paper extends analogically a man's computational power. Through notes, sketches and registers, an individual can solve problems that he otherwise couldn't, such as the accounting of dozens of items, division of large degree polynomials, evaluation of convoluted integrals, solving differential equations, inversion of matrices, and even absolutely shitty things like multiplying big numbers.

Post neuralink zoomers most likely literally won't understand what this means, and this deeply saddens me. How do I cope?

>> No.12132932

I do all my work in ms paint I don't even use pen and paper now.

>> No.12132981

You use Paint like you use pen and paper tho, the process is the same.

>> No.12133037

>How do I cope?
easy, neuralink is never going to work, no one is actually going to get to use it.

>> No.12133038


>> No.12133108


>> No.12133117

What kind of follow up can climate orbiter Akatsuki do at Venus? It's not written about much in Western media and my understanding is that it's not in its ideal science orbit.

>> No.12133139

That's fair, thanks.
Also, thanks for the offer, but I don't really have any other questions.

>> No.12133188

also, my writing on an ipad is dogshit. it's too slippery

>> No.12133315

What are the maximal ideals of [math]R=k[x_1,...,x_n][/math] for a non algebraically closed field [math]k[/math]?
A source says that there is a set theoretic bijection between the maximals over [math]\bar k[x_1,...,x_n][/math] (which consist of the ideals [math](x_1-a_1,...,x_n-a_n)[/math], with [math]a_i\in \bar k[/math]), and the maximals in [math]R[/math], modulo the action of the automorphism group [math]\text{Aut}(K/k)[/math].

Is there a more explicit description? That is, in terms of polynomial generators of the maximal ideal.

>> No.12133395
File: 15 KB, 690x147, Binomial-Distribution-Formula[1].png [View same] [iqdb] [saucenao] [google] [report]

Why exactly do we have the combination formula in the binomial distribution? Intuition helps me to see it but I can't exactly reason through it. It doesn't help that I do have some troubles understanding the derivation of the combination and permutation formula. I can follow the logic of the problems but when it comes to applying the formulas I just get all messed up and don't know how to proceed.

>> No.12133402

because there are multiple ways that you can get x successes in n trials
ex: 2 and 3, s is success f is failure:
s s f
s f s
f s s
thus you need to multiply the probability of getting 2 successes in 3 trials by the number of ways that you can get that (3) to weight it properly

>> No.12133416

the reason we have this term is because the following term, [math] p^x (1-p)^{n-x} [/math] can be interpreted as "the probability of getting x successes followed by n-x failures." That's only one way that you can get x success. The binomial coefficient gives you the number of other possible ways that this number of successes and failures can happen

>> No.12133454

That was a very nice explanation anon. You're good at explaining things, I think that made it quite clear, thank you

>> No.12133462

thank you. I'm always unsure of my teaching skills since I've never had the chance to TA and get feedback. I appreciate it.

>> No.12134204

Slow thread, lads.

>> No.12134220

there are No Questions, don't complain

>> No.12134233

Does a magnetic field interfere with other magnetic fields? Like a wave specifically, is there an interference pattern associated with the magnetic fields around lets say two adjacent magnets

>> No.12134726

Based on our current physics, will it ever be possible to make computers that can send data into the past?

>> No.12134827
File: 560 KB, 2190x1513, IMG_20200918_122832.jpg [View same] [iqdb] [saucenao] [google] [report]

How do i solve 53? If i simplify the upper equation i get 8y+2x=3xy
But if i put the xy=8 from the lower equation to the upper one i get an equation that is not quadratic.
And if i translate the lower equation to x=8/y and put it in the upper one i get x^2=40, that doesn't make sense.
Where did i go wrong here?

>> No.12134843

xy=8 -> x=8/y

8/(8/y)+2/y = y+2/y = (y^2+2)/y = 3
-> y^2-3y+2=0 -> y1=1, y2=2

8/x+2=3 -> x=8
8/x+1=3 -> x=4

>> No.12134913

I have learnt statistics in my own language and now there's a thing I don't know the english name of.
If we have a sample size larger than 10% of the population, we can do "ändlighetskorrektionen" with (1-n/N). The swedish name means something like the finiteness correction but that's not the english name.
Do any of you recognize this and know what to call it in english?

>> No.12134946

I really doubt there is desu.
Specifically, if there was a description, I can't help but picture it as "For every element in the closure's base, associate it to its least divisor in R", except that doesn't work, but in some cases it looks like it does.
For example, the ideal [math]\langle x - i, y + i \rangle \in \bar{Q}[x, y][/math] has an exotic element [math]x + y[/math] in [math]\mathbb{Q}[x, y][/math], but if you change to [math]\langle x- \sqrt{2} i, y + i[/math] it seems like it vanishes and the least degree term kicks upward.

>> No.12135093
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and innumerable negative health problems

>> No.12135133

Can /sci/ clarify just what the heck is information theory all about (specifically the concept of entropy)? You may assume background in undergrad probability theory, measure theory, computational complexity etc. Thanks!

>> No.12135152

Enjoy your:
-erectile dysfunction
-increased risk of cardiovascular disease (haha, yeah heart attacks don't hur- OWOWOWOWOW)
-death by COPD
-poor memory and function due to the microvascular strokes you'll develop over your lifetime (yeap, you read it right, STROKES as in brain death)
-increased risk of cancer (note I didn't specify lung because the carcinogens in cigarettes are linked with many other non-lung cancers)

Oh yes, almost forgot the benefits
+protective if you have Crohn's disease (yeah, sure, go ahead and tell me how you have Crohn's)
+destresses you and keeps you away from depression

The last point is moot because once you develop health complications, you're going to be depressed anyways.

Don't (you) me. There is nothing you can do to argue against this. If you think you have a valid argument, shut the fuck up, go and read the evidence and then maybe, just maybe I'll consider reading your reply.

Also, for anyone who says smoking keeps them stimulated to do their job etc., think about how cucked you are that you're working for 'the man' and he's pushing you to perform beyond your body's natural capabilities that you need an artificial stimulant to keep you going (yes I know coffee counts as one too, fuck all stimulant-requiring jobs).

>> No.12135160

genuine autism

>> No.12135174

It's Bessel's correction, named after Friedrich Bessel.

>> No.12135185
File: 819 KB, 993x699, sgz.png [View same] [iqdb] [saucenao] [google] [report]

>Don't (you) me. There is nothing you can do to argue against this. If you think you have a valid argument, shut the fuck up, go and read the evidence and then maybe, just maybe I'll consider reading your reply.
>Also, for anyone who says smoking keeps them stimulated to do their job etc., think about how cucked you are that you're working for 'the man' and he's pushing you to perform beyond your body's natural capabilities that you need an artificial stimulant to keep you going (yes I know coffee counts as one too, fuck all stimulant-requiring jobs).
I wish you could read this in five years and hang yourself on the fragrant bouquet of shame. The first notes resemble a large co-mingling of cringe and self-righteousness packaged in a family friendly commie anti-smoking message. The under notes are reminiscent of puritan brand vitriol and certainty of purpose, a pleasant effervescence, could it be believing this actually matters and that you aren't a paid shill?
No, it is something different. There is a stinging malingering putrid acceptance of some sort of dogma. While a drug pusher is making money, a pawn is merely cast from the board. What is the game, and who benefits? Is this the salt of youth?

>> No.12135187

just dont, if you really want to get nicotine into your body smoking is literally worst way to do it

>> No.12135210
File: 21 KB, 760x200, Screenshot_20200918-092627.png [View same] [iqdb] [saucenao] [google] [report]

What's up with the colon-equals operator here?

>> No.12135376


>> No.12135575

Right, but why not use the equals sign? I've been through spivak, apostol, and Riley+Hobson+Bence and I've never seen it used, just the equals sign.

>> No.12135631

So I know how to get the answer intuitively using the unit circle but is there any other way to get the answer? It's bothering for no good reason. I know arccos(-1/2) = 2pi/3 but how would I get 4pi/3 in a similar algebraic manner?

>> No.12135639
File: 12 KB, 539x266, 2020-09-18 11_36_16-Window.png [View same] [iqdb] [saucenao] [google] [report]

Forgot pic

>> No.12135648

do you know any calculus? the easiest way is to find the zeros of the first derivative of f(x)

>> No.12135654

Cosine is symmetric around any multiple of [math]2 \pi[/math]]

>> No.12135660
File: 2 KB, 141x67, matrix.png [View same] [iqdb] [saucenao] [google] [report]

the expression on the left is a matrix, right? given values, how do I interpret/check if it equals zero? Do I multiply or add in some pattern?

I thought it could only equal zero if all the values are zero, otherwise it can't be concatenated in a standard way to a single number without an algorithm or operations.

>> No.12135665
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Vent on me about your /sci/ frustrations

>> No.12135669

*Any multiple of [math]\pi[/math] sorry

>> No.12135671
File: 322 KB, 460x690, Houjou.png [View same] [iqdb] [saucenao] [google] [report]


>> No.12135675

My school is closed for the entire next week due to chink flu and it's driving me insane.

>> No.12135685

what were you working on?

>> No.12135687

It was already dogshit to work an entire semester at home last year and it looks like it's not going to be any different this time around.

>> No.12135688
File: 307 KB, 2048x1937, __cirno_touhou_drawn_by_akiyoku__19cc4c64dd70016ff62a333f43d4d999.jpg [View same] [iqdb] [saucenao] [google] [report]

Coincidentally, people have been asking lots of stupid shit in /mg/ lately.
Wanna run a psyop where we pretend to be /mg/ oldfags and tell people there to fuck off to /sqt/?
Because autism.
I'm psychologically incapable of solving literally anything that comes out of the IMO or the Putnam.

>> No.12135701

Why do you dislike working from home?
Have you tried any of the autistic studying methods like study groups?

>> No.12135714

I got all A grades in my freshman year and I will say that at least 50% of that comes from /sqt/ helping and explaining things. I ask stuff here because I don't feel judged, or more accurately, I don't care about feeling judged by anonymous people on a cartoon forum when asking dumb questions.

>> No.12135715

dropped not one but two classes in order to teach this lab, down to 11 hours now and feeling like a chump. i was set to graduate at 22 y/o but now its uncertain. i did it to get close with the prof and hopefully get research experience (which fortunately it seems like he likes me) but its hard making decisions without knowing their outcome, its not like theres anyone to teach you this stuff, you just have to guess and check but instead of a 2nd grade math test its my future :)

>> No.12135718

>Why do you dislike working from home?
Might be an autism thing but I feel far more compelled to pay attention and get involved when I'm physically participating in classes than in Zoom conferences.

>> No.12135739

I honestly believe talking to the correct people is way more important than graduating or having some A or diploma or whatever
I would indeed recomend getting close to academics and workers with experience
Well, just a few share of people are actually accomodated to the model of listening and copying like most schools do. Most people just has workarounds to get passing grades despite the monotony
try looking up studying methods

>> No.12135740
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>Have you tried any of the autistic studying methods like study groups?
Thanks for the advice, but I don't actually care enough to do more than whining.
I'm like that too, so it's probably an autism thing.

>> No.12135748
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care, or else

>> No.12135763
File: 211 KB, 602x535, delete this.png [View same] [iqdb] [saucenao] [google] [report]

Or else what?

>> No.12136101
File: 531 B, 32x22, Screenshot_20200918_140214.png [View same] [iqdb] [saucenao] [google] [report]

does anyone know what this symbol in discrete logic?

>> No.12136107

i am talking about the star thing never seen it before and Wikipedia doesn't seem to have it

>> No.12136345

As has been mentioned, it's a determinant. It will be equal to zero if the three 2D points (x0,y0), (x0',y0') and (x1,y1) are colinear.

FWIW, it expands to
x0'y1 - x1y0' - x0y1 + x1y0 + x0y0' - x0'y0 = 0

>> No.12136447

I can't go into lab and my project is fucking shit.
I love my lab and find the work super interesting and I know my project has to be done in order for the experiment to work, but fuck it's so dry. It's not going to lead to any publication, it's just necessary.
Meanwhile I'm watching all my peers who joined at the same time start to push out papers. Shit really sucks.

>> No.12136903

Are most steps in the lithographic process for CMOS fabrication a repeat of:
>lay down some material
>apply photoresist
>apply mask + UV
>shadowed or unshadowed regions are dissolved depending on negative or positive photoresist
>etch exposed regions
>remove remaining photoresist

With some possible steps in between like CVD deposition of oxide? My professor sucks at explaining shit and the book is kind of vague about steps after the STI/well implantation.

Also, initially is the silicon wafer completely doped to be either p/n type (depending on whether the desired substrate is p/n type) or are some regions left as raw silicon?

>> No.12136928

It has no rigorous definition as it isn’t math and so has no axioms or formal structure and isn’t physics so it doesn’t describe the natural world. This post will have retarded seething nigger cope replies but i’m correct and always will be.
Read more math, stop being a retarded faggot. It’s used constantly to define objects.
I haven’t read any papers I’m interested in for over 2 months, have no idea what I want to work on and probably am a bit of a push over when it comes to my interests. I also hate anime posters like you.

>> No.12136948

>Are there no EEs here?
Anime posting anon on here knows every subject there is to know, so if he is around he will answer. He's one of the legitimate smart and knowledgeable people on /sci/.

>> No.12136962
File: 69 KB, 600x555, 2d2887a5c1e04b57ec52eab5c7718f2e6.jpg [View same] [iqdb] [saucenao] [google] [report]

I don't know literally anything about electrical engineering.

>> No.12136979

You literally do.

>> No.12137005

It's been a couple hours and no one has given a serious answer, so I'll try my hand at it:
I tell you that a random variable has assumed a certain value. Say, that a dice fell on six. This is information.
We want to quantitatively measure the information given by saying that an event happened. This function, [math]I[/math], naturally only depends on the probability of the event happening, so we can write it as [math]I(p)[/math]. Also, if I tell you that an event of probability [math]p[/math] and an independent event of probability [math]q[/math] has also happened, the information I've told you is naturally the sum of the two individual pieces of info, and also the information associated to an event of probability [math]pq[/math] happening, and this nets us [math]I(pq) = I(p) + I(q)[/math].
Because probabilities are always positive numbers smaller than one, we're led to consider [math]I(p) = \log _2 \frac{1}{p} = - \log _2 p[/math].
Entropy measures, on average, how much information an event gives you, and is associated to a random variable.

Most of this knowledge comes from me reading Information Theory for Electric Engineers this morning.

>> No.12137009
File: 217 KB, 880x900, thinkingkon.png [View same] [iqdb] [saucenao] [google] [report]

I work as a software engineer. Making really good money. I very much could continue at my current pace and retire comfortably at 45/50. I'm on track to senior and I foresee my income increasing year over year. I work mainly with distributed systems - mostly building components & producing designs to solve scaling problems. I feel that I have stagnated - most of my days are spent doing difficult yet menial work.

I have a dream. It's to become an academic & produce research. A /sci/ientist. Both my parents are PhDs and it feels wrong that I stopped at my bachelor's degree. Another reason I want to become an academic is because I am genuinely interested in some things, such as the study of complexity, graph theory, & distributed consensus. However, my golden handcuffs prevent me from doing so. I have a few questions

- Do people successfully become academics in their 40s? I can become financially independent by then, but as I understand it intelligence drops off and I'm worried my age will prevent me from contributing anything meaningful
- Do you guys know of people who find research opportunities as engineers, and branch out from there?
- Is it possible to do high tier personal projects, get published in journals as an independent? I could produce projects and publish it under my own name. Would that be enough to work for a research wing of a company?

>> No.12137047

>how do you calculate the sop or karnaugh map for a system with more than 5 inputs with more than 10 bits total
Karnaugh maps are useful only for few inputs to do some quick minimizations by hand. For more inputs there are better methods like Quine–McCluskey algorithm. But even they have a limited use because this is a NP-complete problem.

>> No.12137129

I was trying to look for a proof of splitting fields of separable polynomials being Galois extensions, and came across this question https://math.stackexchange.com/questions/1662557/if-e-is-the-splitting-field-for-an-irreducible-separable-polynomial-over-f-t?rq=1

For the most part it makes sense to me, but there's this part that says:
Let [math] p_{i} (x) \in F_{i} [x] [/math] be the minimal polynomial of [math] a_{i} [/math] over [math] F_{i} [/math]. Since [math] p_{i} \text{ and } p [/math] both have [math] a_{i+1} [/math] as a root, we have [math] p_{i} | p [/math] and therefore [math] p_{i} \text{ has } d_{i} [/math] distinct roots in E

And I have no fucking clue about where most of this even comes from, so my questions are:
Why do [math] p_{i} \text{ and } p [/math] have the root [math] a_{i+1} [/math] in common?
How does having one root in common imply that [math] p_{i}|p [/math]?
Wouldn't [math] p_{i} [/math] having [math] d_{i} [/math] distinct elements in E only hold true if [math]a_{i+1}[/math] was a primitive element?

For the first question I honestly just think that the guy messed up in his statement and meant to say "Let [math] p_{i} (x) \in F_{i} [x] [/math] be the minimal polynomial of [math] a_{i+1} [/math] over [math] F_{i} [/math]", because from the way he defines [math] F_{i} [/math] I'd imagine the minimal polynomial of [math] a_{i} [/math] would just be [math] x-a_{i} [/math], but maybe I'm just stupid and don't understand
And the second question I guess makes sense because p is irreducible over F, but I don't know how to write it down more formally

>> No.12137222

If I'm given a probability mass function of [math]f(x) = \frac{x}{15}[/math] for [math]x = 1 , 2 , 3 , 4 , 5[/math], is the cumulative distribution of [math]X[/math] just given by [math]\int _{1} ^{+ \infty} f(x) dx[/math]?

>> No.12137245

Youre given a pmf and X is a discrete random random variable. The cumulative distribution function is the summation of all values before the given x value. Don't integrate because the integral is zero. If you have a continuous random variable, that integral is wrong because it will always give a fixed number. The cumulative distribution function is a function, so it needs to vary with x, and the variable is the upper bound of integration.
[math] F_X(x) = \sum_{n\leq x} f(x).[/math]

>> No.12137250

Thank you.

>> No.12137382

>Why do p_i and p have the root a_i+1 in common?
They don't, actually. The minimal polynomial of [math]a_i[/math] over [math]F_i[/math] is just [math](x - a_i)[/math], you're entirely correct.
>How does having one root in common imply that pi|p?
Minimal polynomial's defining property.
>Wouldn't pi having di distinct elements in E only hold true if a_i+1 was a primitive element?
I don't follow.

>> No.12137434

Oh okay so if what I mentioned about the guy messing up and meaning to write that [math] p_{i} [/math] is the minimal polynomial of [math] a_{i+1} [/math] instead is correct (as opposed to [math] a_{i} [/math] which just has a linear minimal polynomial), then I can see the second part being true, I completely forgot about checking the definition with that case
>I don't follow.
I mean, as far as I understand (for finite extensions at least), [math]d_{i} = [ F_{i+1} : F_{i} ] [/math] implies that the minimal polynomial of a primitive element of the extension is of degree [math] d_{i} [/math] (and thus has that amount of roots). From the definition of [math] F_{i+1} [/math], I think we could just write it as [math] F_{i} (a_{i+1} )[/math] and turn it into a simple extension of [math] F_{i} [/math] so that still holds, I guess I was confused because I didn't understand why [math] a_{i+1} [/math] was a root of [math] p_{i} [/math] to begin with so the rest just didn't make much sense to me

>> No.12137532
File: 192 KB, 600x641, d2d8d788a16d063a0ef78f66260b05da1.jpg [View same] [iqdb] [saucenao] [google] [report]

>even Tooker is in the RBG sticky

>> No.12137784

I have an IQ of 139 but have been out of school for 10 years and never progressed past algebra. I'm going to need to brush up on my academics because my memory of some things has faded. Will I be able to make it through Aerospace Engineering? I've sort of formulated a plan to start in a Junior College in order to learn Trig, Precalc and Calc and such prerequisites. Afterwards I plan on transferring to a university with a competitive Aerospace Engineering program. Is my goal achievable or am I going to screw myself?

>> No.12137788

>I have an IQ of 139
Stopped reading here.

>> No.12137943

I know I've already asked if I should double major in Applied Math and Linguistics in one of these threads before but I want to ask: What are the best fields where having a degree in applied math and a degree in linguistics is advantageous? I asked in /mg/ and the answer seems to be in natural language processing, and I'm also interested in speech synthesis. The issue is that I'm kind of apprehensive about AI and AI-adjacent fields because I'm worried about the unethical uses of it (such as how you might need to farm data in order to produce sample data for speech synthesis, for example).

>> No.12138022

Do TAs usually help with homework problems? ive never had to go to office hours for previous courses but one of them is brutal now and i have no idea what to do so i will probably go to his office hours

>> No.12138040

If they have office hours, then they'll help you with homework or any questions relating to the class. That's why they're there.

>> No.12138345

How do scientists know what journal to submit their paper to? For every subfield there are half a dozen or more journals, and usually you can't submit your findings to more than one journal at a time. Do they just go "Okay, this is the highest IF journal that will give me a chance"?

>> No.12138481

Cheers anon, that was short and to the point.

>> No.12138526

has three solutions:
wolframalpha only gives 2 answers with the simple input of z^2-2z=0
how do you command WA to show the 1-i ?

>> No.12138642

nvm, im an idiot

>> No.12138790

What's a good physics text to go through while learning calculus? Just little more than a month into calc 1.

>> No.12138820

Can someone recommend a book on physics with a gentle treatment of tensors? (None of that abstract stuff). Just need some examples and use cases on the undergrad level, as basic as possible.

>> No.12138854


>> No.12139315


>> No.12139319
File: 3 KB, 933x399, moment.png [View same] [iqdb] [saucenao] [google] [report]

Given the moment of the rectangle about point B, is it possible to find the moment of the rectangle about point A?

>> No.12139553

No. Consider a simpler case: a point mass m at a distance r from B; I=m*r^2. Halving r but increasing m fourfold leaves the moment of inertia about B unchanged, but the moment of inertia about some point far from B would increase roughly fourfold.

>> No.12139640
File: 185 KB, 341x320, Oscillating_pendulum.gif [View same] [iqdb] [saucenao] [google] [report]

redpill me on pendulums

>> No.12139698

What do you want to know

>> No.12139789
File: 13 KB, 629x157, snipsnap.png [View same] [iqdb] [saucenao] [google] [report]

Requesting a slick, satisfying proof of this.
Example of non-slick, dissatisfying proof:
[math]\text{There is an } x' \text{ and a } y' \text{ such that } x' \neq y' \text{ and } K(x', y') \neq 0. \\ \text{Then we can take a bump function } f \text{ centered on } y' \text{ such that } f(x') = 0. \\ \text{If necessary, we can pass to } g(x) = f(y' + \epsilon (x - y')) \text{ for large epsilon to guarantee that the integral doesn't zero, q.e.d.}[/math]

>> No.12139830
File: 73 KB, 1272x532, 1.png [View same] [iqdb] [saucenao] [google] [report]

How would I go about calculating [math] V(N_p|\tilde{N_p})[/math]? I know by definition that [math] V(Y|X)=\sum (y-E(Y|X)^2\times P(Y|X) [/math]. So should I simply calculate [math] (1-[p+(1-p)(1+\tilde{N_p})])^2\times p + (1 + \tilde{N_p}-[p+(1-p)(1+\tilde{N_p})])^2\times (1-p) [/math]?

>> No.12139966

When dealing with chaotic systems, small angle approximation doesn't work anymore.
Is that redpilled enough?

>> No.12139976

Whatever happened to Yukarifag? God I miss that faggot...

>> No.12139997

What's the name of the paradox with the turtle?

>> No.12140004

achilles and the tortoise?

>> No.12140008
File: 47 KB, 672x505, unknown-79.png [View same] [iqdb] [saucenao] [google] [report]

can someone please tell me how they got delta A of k and f(xk, yk)? I've spent an hour on this and my head hurts

>> No.12140109

Zeno's paradox

>> No.12140130

They bullied him off the board, this used to happen to anyone annoying on any board before the reddit colonization.

>> No.12140140
File: 355 KB, 864x770, __hata_no_kokoro_touhou_drawn_by_rakkidei__ac85f263f3bc5a3064c0317a71133ace.jpg [View same] [iqdb] [saucenao] [google] [report]

Conjecture one:
He got bored and fucked off.
Conjecture two:
Whenever he thinks about /sqt/ he recalls this >>https://warosu.org/sci/thread/S11475807#p11484606 or a similar event and, because he later understood why he was wrong on an absolutely basic level, feels literally too embarassed to show his face here.
Yukarifag, if you're reading this, I forgive you, everyone forgives you, come home. I post as much if not more retarded shit than you, I just eventually learned not to attach 2hus when I'm not at least 95% confident on what I'm saying.

>> No.12140249

What causes seasonl depression and is there any way to mitigate it? I just realized that today I've just been depressed a lot more than usual... Kinda just want to sleep forever despite having a bunch of tasks to do!

>> No.12140324

Who was in the wrong here?

>> No.12140371

so why do you people willingly deanonymize yourself on an anonymous board! why do you this to yourself? you can just earn points on stackoverflow or physicsforums or reddit. and maybe you do. but the whole point of 4chan is a stress free interaction and you should be able to post retarded shit without feeling any remorse and thats what anonymity gives you which you choose to reject!

>> No.12140383

Because they get used to generally being correct and helpful about things, and they take the avatar to be a signal of their authority.
It's pretty sad. He literally said it in the post, that he uses a 2hu when he's confident in his answer.

>> No.12140385

>what causes seasonal depression
being sad
>how do i mitigate it
be happy instead

>> No.12140401

the need for social validation is more fundamental than the instinct towards higher reason. even autistic homosexual geometers cannot resist

>> No.12140407
File: 889 KB, 2321x3583, 143ea0cc6fe8ce7fded1eff2c256123a3.jpg [View same] [iqdb] [saucenao] [google] [report]

This >>https://warosu.org/sci/thread/S11475807#p11484595 guy was either wrong for using "vector space" to refer to "topological vector space" or he was just plain wrong.
>inb4 dude it's implicit when he mentioned metrizability that he means topological vector spaces
No, because, get this:
He said before hand that not every vector space is a Banach space. And that's literally correct as is, see http://user.math.uzh.ch/halbeisen/publications/pdf/hamel.pdf , Lemma 3.4. Even without a topology there are completely algebraic obstructions to Banach space structures, and a space like the real vector space with countable base admits no Banach space structure.
Also, topological vector spaces weren't even relevant to the discussion, what the fuck dude.

I don't understand a single post Yukarifag made, but, even in hindsight months later, they still read like nonsense.

Thus, I was right, everyone else was wrong, q.e.d.
I post Remilia because she's extremely cute.
I post other 2hus so Remilia mixes in.
If you don't want me to be recognizable, feel free to post as many Remimis as you want and pretend to be me. You can grab some here: https://safebooru.donmai.us/posts?tags=remilia_scarlet+

>> No.12140479
File: 906 KB, 1500x1400, Patchouli Knowledge reading Riemannian geometry.png [View same] [iqdb] [saucenao] [google] [report]

Thoughts on Patchouli Knowledge?

>> No.12140519

Keep posting remilia bro, I love her and I love you

>> No.12140557
File: 12 KB, 636x44, Screen Shot 2020-09-19 at 8.30.40 PM.png [View same] [iqdb] [saucenao] [google] [report]

If we take [math]f = 0[/math], that means there is no movement in either the positive or negative x direction, right?

>> No.12140561

bro we have literally no idea what you're talking about
I'm trying to understand this question and the best I can do is that it's some sort of mass on an inclined plane? you need to explain it better

>> No.12140573

I'm assuming f is the frictional force so the inclined plane assumption is probably corect.

>> No.12140576
File: 37 KB, 532x232, Screen Shot 2020-09-19 at 8.36.38 PM.png [View same] [iqdb] [saucenao] [google] [report]

Sorry, basically we have the system of pic related and the forces for the x direction (positive is left; negative is right) is [math]m_1 g + f - Mg sin (\alpha) = 0[/math] and the y direction (positive is up; negative is down) is [math]N - Mg cos(\alpha) = 0[/math].

I'm interested in the case where f = 0.

>> No.12140596

f=0 just means the frictional force is 0. that means there's no coefficient of friction between the block M and the plane, or the force from the hanging mass m is exactly enough to cancel gravity in such a way that there's no friction for that reason

when you set up the equation [math]mg+f-Mg \text{sin} \alpha=0 [/math] you're claiming that there is no x force and thus no x acceleration. setting f=0 doesn't impact this, you can have f !=0 and it would still not be accelerating in the x direction because the total x forces are 0.

also, don't forget that 0 force doesn't mean 0 movement, it means 0 acceleration. if your system is starting at rest it will not move, but if it starts off moving then it will be moving in the x direction, just not accelerating.

>> No.12140611

That makes sense.

>> No.12140696

Is the tangent vector of a function in 3d the same as its velocity vector? So if they ask me for the tangent vector, I just differentiate the position vector?

>> No.12140716

If you're given a position vector [math]\overrightarrow{p} (t)[/math], then the tangent vector at [math]t_0[/math] is [math]\overrightarrow{p'}(t_0) = \overrightarrow{v}(t_0)[/math].

>> No.12140721
File: 206 KB, 801x600, Higurashi.no.Naku.Koro.ni.full.179959.jpg [View same] [iqdb] [saucenao] [google] [report]

im pretty sure im the only one here that posts satoko so if you see a post with satoko you know its me c:

>> No.12140728

avatarfagging is against the global rules.

>> No.12140733


>> No.12140738

If only.

>> No.12140801

>If you don't want me to be recognizable
Where did I say that?? Thats not what I asked at all. I actually like to know that it is you. I love it. I asked how YOU feel about that. My point is it may feel pretty stressful to be recognizable on an otherwise anonymous board. But if you like it that people like it that you are recognizable, then it makes sense.

>> No.12140814

it is explicitly prohibited per the global rules.

>> No.12140816

so are half the threads on this godforsaken board. does that mean anything?

>> No.12140828

do you, personally, have some sort of issue against the images posted in this thread? why dont you just speak your mind like a man? because bringing up the rules makes you look like a tool

>> No.12140911

So I'm back at school and taking calc 2, but I ran into a problem I've had trouble solving.

Prove that
\frac{1}{4} \int f(x) dx = \int \frac{1}{2}f(2x)dx

Is that just because you can u-sub into
\frac{1}{4} \int f(u) du


can I just treat [math] \int f(u)du [/math] as [math] \int f(x)dx [/math]?
They come out to the same answer in a definite integral because you need to replace the bounds of integration. So can I assume that they are equal in an indefinite? Logically I just think of it as the same thing written differently in this case. But my intuition probably isn't very good.

>> No.12141092

i think you may have copied the problem down incorrectly

>> No.12141109
File: 5 KB, 416x63, pic.png [View same] [iqdb] [saucenao] [google] [report]


>> No.12141159

yep just sub u = 2x
you can then replace f(u)du with f(x)dx

>> No.12141214
File: 617 KB, 590x393, file.png [View same] [iqdb] [saucenao] [google] [report]

How do ants solve the trolley problem?

>> No.12141223
File: 79 KB, 600x422, FpJvg.jpg [View same] [iqdb] [saucenao] [google] [report]

What is it called when you're trying to prove something that's not a theorem? Like something along this format but you have to prove if the conjecture is true or false? (basically what word to replace Theorem with).

>> No.12141246


>> No.12141252

I hate avatar fags, if there is a means to harm them or dissuade them from posting I'm more than happy to make use of it. Destroying one's enemies by any and all means is masculine, is the very essence of warfare. You are a faggot and a coward and I would love to watch you die in agony.
They should be permabanned from breaking global rules repeatedly and encouraging others to do the same. This is an anonymous image board for discussing the on-topic interests of the specific boards the user finds themselves on. Bringing personal identity into the fore is disrespecting the core mandates of the site. They are worse than spammers and political warriors, they are threatening anonymity and should be punished severely, bullied incessantly, driven from the site.

>> No.12141254

thank you fren

>> No.12141257

Theorem: Conjecture is true/Conjecture is false.
Proof: The proof goes here.

>> No.12141276

It's not that big of a deal, bro.

>> No.12142051

Patcho is cute.
Note taken.
I don't, I'd sooner everyone drown this place in Remimis so I mix in.
However, I'm willing to accept being recognized for the greater good.

>> No.12142181

>I'd sooner everyone drown this place in Remimis so I mix in.
This is the most horrible thing that could ever happen to someone who cares about their reputation. I didn't want to mention that but since you brought it up, some prankster can start posting dumb shit from your name. It is equivalent to being hacked. You don't want that. We should really stop talking about this. I only wish you the best and I don't want to give anyone any ideas. This place is full of idiots and with posters like you or that other anime poster gone, it will be just IQ and /pol/ threads.

>> No.12142213

I had a dream that 4chan was shut down for good. And I felt literal shock and disbelief and wanted to share the news with someone but I suddenly realized I dont know anyone who I can even talk with about this site and everyone I knew from this site is suddenly gone and I have no way to find them. So in my dream I broke the news to real people I know and they were giving me signals like shhhhh stop talking about this in presence of "other people" so it is as if I knew that some people I know might browse this place but I never asked and I just wanted to share the pain with them in a discreet way. Anyway my reaction seems surprising because I always thought that I had an unnecessary addiction to to this place and it would be a huge relief to stop browsing it and I wouldn't even look back. However based on my reaction in my sleep that would not be the case. Now the stupid question: can our reactions in our dreams be considered real life testing of a hypothetical situation where you don't know how you are going to react to certain news? Or it is bs and your reactions could be totally different when that happens for real? How "true" and "real" are our thoughts in our dreams? Wonder if anyone ever researched that.

>> No.12142280

suppose you have an object traveling 1 km/s and which blinks a light every second, and it travels toward you.

what will you perceive its period to be and why?

>> No.12142285

the object is traveling 1 km/s in its own frame of reference *

>> No.12142291
File: 38 KB, 362x346, 1593273044273.jpg [View same] [iqdb] [saucenao] [google] [report]

>Work in hypothesis for 2 years
>Might have come up with something that makes my previous paper obsolete
Did I just BTFO myself and rendered my past 2 years self useless

>> No.12142315

The reception period would be almost indistinguishable from the emission period, because [math]\frac{v}{c} << 1[/math].

>> No.12142317
File: 83 KB, 922x593, 1.png [View same] [iqdb] [saucenao] [google] [report]

Stack exchange isn't being helpful, so I am coming in a time of need to you anons. The problem is actually pretty interesting but I am too brainlet to figure it out. How do I find [math] S_n [/math] with the given information?

>> No.12142323

would the period be larger or smaller than 1 second

>> No.12142338

Very slightly larger.
[eqn]f_{rec} = \sqrt{\frac{1-\beta}{1+\beta}}f_{em}[/eqn]
with [math]\beta = \frac{v}{c}[/math]

>> No.12142363

suppose the object is 100 km away
the first blink would be received after 1 second + 100km/300,000km = ~1.000333s
the second would be received after 2 seconds + 99km/300,000km = ~2.00033s
the third after 3 seconds + 98km/300,000km = ~3.000326
and so forth
3.000326 - 2.00033 = 0.999996

so why would it not appear to decrease from observer's perspective?

>> No.12142410
File: 25 KB, 995x424, why.png [View same] [iqdb] [saucenao] [google] [report]

mathlet here, I know the centroid "should" be at 2pi/r to work for the surface area of a sphere using Pappus's theorem, but how do you calculate it as such. Keep getting/seeing 4r/3pi.

>> No.12142441


Learning chemistry has this weird learning curve where you're learning physically advanced stuff without getting any basic physics. If you want to really understand what you're doing focus on physical chemistry.

To answer your question: applying an electric field attracts and repels ions depending on their charge.

>> No.12142459
File: 27 KB, 700x467, Smiling British Pepe.png [View same] [iqdb] [saucenao] [google] [report]

>Keep getting/seeing 4r/3pi

That's the centroid of a solid/filled semicircle. You need to use the centroid of a semicircular arc to find the surface area of a sphere.

>> No.12142486

That's literally just a binomial distribution: [math]p = \pi / 4[/math], [math]n[/math] is the number of points. Can't you get the minimum [math]n[/math] needed from google?

>> No.12142491

I can't just google, no. I need to calculate [math] n [/math] required by using the given bounds.

>> No.12142541
File: 86 KB, 965x452, unknown-130.png [View same] [iqdb] [saucenao] [google] [report]

Can someone tell me how they got from the second last step to the last? I don't know how they pulled out the (y+y')...

>> No.12142619

>Also, every real/complex vector space is metrizable by a norm.
>Take a base. The norm of an element is the sum of the modulos of it's coefficients in the base.

My God it hurts to read that.

>> No.12142643
File: 725 KB, 709x1200, 91dd7cd0225428f0395c78b306625127.png [View same] [iqdb] [saucenao] [google] [report]

[math]y+y'=1[/math], same way they knocked out the [math]x+x'[/math] term in the previous step

>> No.12142652

sorry i don't know anything about anime. isn't this yukari? so yukari is back?

>> No.12142655

no thats not yukari

>> No.12142676
File: 601 KB, 1548x877, Yukaristop.png [View same] [iqdb] [saucenao] [google] [report]

Are you aware of what Google is?

>> No.12142750

Ah christ of course, thanks. I knew it had to be something simple

>> No.12142791

and how is that different? same color palette of pinkish colors, same everything.

>> No.12142793

also i am not googling that for the fear of death. google will remember that i am interested in anime. i'd have to use vpn for that.

>> No.12142831

you mind rereading that and posting something else? the green dressed, blond haired girl isnt pinkish

>> No.12142885

Does MEK react in any way with LCP plastic? What is a good resource for finding out information such as this? Calling the manufacturer?

>> No.12142946

if [math]A\subset B[/math]
then [math]\exists x (x\in A\Rightarrow x\in B)[/math]
Why isn't this an appropriate answer? It seems to me that 'there exists' should be a subset of 'for all' and thus an acceptable answer?

>> No.12142954

exists isnt a "subset" of for all
there exists an x with 1 = x = 0
for all x with 1 = x = 0 we have P(x)
theyre totally different

>> No.12142964

>'there exists' should be a subset of 'for all'
It shouldn't.

>> No.12142967

what do you mean by 1=x=0?

>> No.12142983

consider the case where [math]A={ }[/math]

>> No.12142987

1=x AND x=0

>> No.12143001

new thread

>> No.12143949

no one?

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