/sqt/ /qtddtot/ - stupid questions thread

[Anonymous No.12128061]

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.
>books?
libgen.is (link might break)
https://stitz-zeager.com/
>journal articles?
sci-hub (you'll have to google for a link, unfortunately)
>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
>how do I post math symbols?
https://i.imgur.com/vPAp2YD.png (and see first reply)
>how do I successfully post math symbols?
https://imgur.com/a/pxKrrdO
>a google search didn't return anything, is there anything else I should try before asking the question here?
https://scholar.google.com/
>where do I look up if the question has already been asked on /sci/?
>>>>/sci/
https://boards.fireden.net/sci/
>how do I optimize an image losslessly?
https://trimage.org/
https://pnggauntlet.com/

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

Stuff:
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
https://pastebin.com/SmBc26uh
Graphing: https://www.desmos.com/
Calc solver: https://www.wolframalpha.com/
Tables, properties, material selection:
https://www.engineeringtoolbox.com/
http://www.matweb.com/

[Anonymous No.12128104]

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.

[Anonymous No.12128125]

>>12128044
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.

[Anonymous No.12128174]

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.

[Anonymous No.12128242]

>>12128174
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.

[Anonymous No.12128254]

>>12113957
oxidation
>>12119726
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?

[Anonymous No.12128258]

>>12128174
E_pot=kx^2
highest displacement -> highest potential energy
Also v=0 at (a), so E_kin=0

[Anonymous No.12128291]

>>12128242
>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?
>>12128258
>highest displacement -> highest potential energy
Got it, highest displacement in terms of amplitude (ym).

Thank you both so much!

[Anonymous No.12128335]

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

[Anonymous No.12128339]

>>12128335
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.

[Anonymous No.12128342]

>>12128339
whats her number

[Anonymous No.12128343]

>>12128335
Marlboro reds.

[Anonymous No.12128347]

>>12128339
>Smoking bad
Absolute reddit take.

[Anonymous No.12128348]

>>12128342
Go ahead and smoke, if you're that retarded to pick it up then you deserve the abysmal death that almost every smoker experiences

[Anonymous No.12128352]

>>12128339
>10 years
i only got 2 more years of undergrad + 7 years for phd so im in the clear

[Anonymous No.12128363]

>>12128348
There is nothing wrong with smoking, though.

[Anonymous No.12128385]

>>12128363
>>12128352
>>12128347
>>12128335
>t.

[Anonymous No.12128389]

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?

[Anonymous No.12128454]

>>12128385
Not an argument. Smoking is linked to many positive health benefits.

[Anonymous No.12128559]

>>12128061
>>12128104
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.

[Anonymous No.12128644]

>>12128559
yeah next time I'll put more work into tweaking it. there's a lot of info, I might condense it a bit

[Anonymous No.12128651]

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.

[Anonymous No.12128689]

>>12128651
[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.

[Anonymous No.12128694]

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

[Anonymous No.12128704]

>>12128694
[math] \frac{2}{\sqrt{3}} [/math]

[Anonymous No.12128740]

>>12128689
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.

[Anonymous No.12128745]

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.

[Anonymous No.12128759]

>>12128745
decision matrix

[Anonymous No.12128788]

>>12128759
Nah, that's too specific

[Anonymous No.12128795]

>>12128788
then it's just a type of table
pic related when you google 2D table

[Anonymous No.12128796]

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

[Anonymous No.12128802]

>>12128796
it would be helpful if you described what the problem was so we didn't have to read your mind

[Anonymous No.12128825]

>>12128796
What are we even looking at?

[Anonymous No.12128833]

>>12128796
Like, I can read the thing.
I literally just don't know what it is you want to do.
>>12128825
Water falls in big circle and leaves through small circle.

[Anonymous No.12128907]

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

[Anonymous No.12128914]

>>12128907
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.

[Anonymous No.12128921]

>>12128914
This but unironically.

[Anonymous No.12128925]

>>12128914
>>12128914

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

[Anonymous No.12128931]

>>12128921
my post was unironic
>>12128925
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.

[Anonymous No.12128934]

>>12128925
I majored in math and minored in Korean, for what it's worth.

[Anonymous 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

[Anonymous No.12128955]

>>12128802
>>12128825
>>12128833
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)

[Anonymous No.12128960]

>>12128948
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

[Anonymous No.12128965]

>>12128955
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?

[Anonymous 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]

[Anonymous No.12128978]

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

[Anonymous No.12129026]

>>12128978
[math]a_1 = 1, a_2 = 4, a_3 = 9, b_1= a+b, b_2 = c, b_3 = a+b+c [/math]

[Anonymous No.12129028]

>>12129026
kill me now. ty

[Anonymous No.12129030]

>>12129026
Based.

[Anonymous No.12129036]

>>12129028
>kill me now
No, no, this is some real schizo wild guessing shit, there's really no shame in getting stuck.

[Anonymous No.12129050]

>>12129036
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.

[Anonymous 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.

[Anonymous No.12129084]

>>12128960
I'm confused. So say I'm "*" and "0" is my house, I start 5 meters to the left of my house
So

* - - - - 0 + + + + +

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

[Anonymous No.12129094]

>>12129050
And by even easier I just mean the same thing. Oy.

[Anonymous No.12129103]

>>12129084
what?
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?

[Anonymous No.12129120]

>>12129067
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.

[Anonymous No.12129134]

>>12128125
That’s not really answering the question. You can’t recombine ad Infinitum. My question was how are LED able to continuously do this.

[Anonymous No.12129139]

>>12129134
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.

[Anonymous No.12129149]

>>12128704
How would you calc this without trig / a computer?

[Anonymous No.12129156]

>>12129149
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.

[Anonymous No.12129161]

>>12128389
Just define it to be ground or 0 volts.

[Anonymous No.12129198]

>>12129156
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

[Anonymous No.12129207]

>>12129103
>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

[Anonymous No.12129210]

>>12129198
no matter how you do it you'll get the same answer
look up how to calculate distances in 3D

[Anonymous No.12129217]

>>12129207
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?

[Anonymous No.12129227]

>>12129217
Okay thank you

[Anonymous No.12129307]

>>12129149
https://en.wikipedia.org/wiki/Euclidean_distance#Three_dimensions

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.

[Anonymous No.12129316]

>>12129307
>for a cube of length [math]l[/math]

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

[Anonymous No.12129407]

>>12128061
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

[Anonymous No.12129410]

>>12129407
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

[Anonymous No.12129445]

>>12129410
What about stuff like this?
https://www.quantamagazine.org/physicists-debate-hawkings-idea-that-the-universe-had-no-beginning-20190606/

[Anonymous No.12129455]

>>12129445
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

[Anonymous No.12129503]

>>12129455
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

[Anonymous No.12129515]

>>12129503
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

[Anonymous No.12129538]

>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

[Anonymous No.12129577]

>>12129538
you're probably doing other shit every day
remove the ability to do those things. get rid of your internet access

[Anonymous No.12129606]

>>12129515
>nobody
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

[Anonymous 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.

[Anonymous No.12129991]

>>12129606
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.

[Anonymous 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

[Anonymous No.12130440]

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

[Anonymous No.12130488]

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

[Anonymous No.12130663]

>>12128104
Pls respond
>>12115337 # || mathematical physics

[Anonymous No.12130689]

>>12128061
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?

[Anonymous No.12130717]

>>12130689
Nevermind, I get it. Geeez, that's such an awkward way of getting to the dy/dx bit,

[Anonymous 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?

[Anonymous No.12130857]

arccos() isn't distributive, right?

[Anonymous No.12130946]

>>12130857
Do you mean linear?
No

[Anonymouse No.12130947]

>>12130857
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.

[Anonymous No.12130958]

>>12130946
it is up to the first order approximation

[Anonymous No.12131005]

>>12129991
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
Ok
>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

[Anonymous No.12131610]

>>12128061
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

[Anonymous No.12131636]

>>/sci/thread/S12005353#p12038383
I'm not sure if this was referring to me, but if it was, I'm listening.

[Anonymous 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

[Anonymous 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.

[Anonymous No.12131705]

>>12130294
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

[Anonymous No.12131712]

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

[Anonymous No.12131713]

>>12130856
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?

[Anonymous No.12131720]

>>12131005
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."

[Anonymous No.12131729]

>>12131712
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

[Anonymous No.12131734]

>>12131713
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

[Anonymous No.12131738]

>>12131610
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.

[Anonymous No.12131743]

>>12131738
yes stationary

[Anonymous No.12131762]

>>12131698
Rewrite as [math](g_y - g_x)U_x = 0[/math].
The solutions should mostly be constant in terms of x.

[Anonymous No.12131772]

>>12131762
>>12131698
Ah fuck I mistyped it
What I meant to type was:
gyUx - gxUy = 0

[Anonymous No.12131773]

how do I find h
please don't laugh

[Anonymous No.12131782]

>>12131772
You just want *some* non-trivial U? Because U=g works.

[Anonymous No.12131786]

>>12131782
Yes exactly. I even guessed that would be the answer, I just can't figure out the actual working to get to it

[Anonymous No.12131795]

>>12131786
>>12131762
What I mean is, is how do I work towards the solution U=g without assuming its that in the first place?

[Anonymous No.12131800]

>>12131795
Meant for>>12131782

[Anonymous No.12131812]

>>12131773
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?

[Anonymous No.12131820]

>>12131786
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.

[Anonymous No.12131834]

>>12131743
>>12131610
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.

[Anonymous No.12131835]

>>12131820
Rather than a symplectic form, it might be easier for you to think of the determinant of
[eqn]\begin{pmatrix}
g_y & g_x \\
U_y & U_x
\end{pmatrix}[/eqn]
See? only zeroes when one is a multiple of the other.

[Anonymous No.12131840]

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

[Anonymous No.12131848]

>>12131835
>>12131820
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.

[Anonymous No.12131859]

>>12131639
Are there no EEs here?

[Anonymous No.12131871]

>>12131772
[eqn]
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}
[/eqn]
So basically you want the cross product to be 0, which means U and g must be orthogonal

[Anonymous No.12131882]

>>12131848
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.

[Anonymous No.12131893]

>>12131610
>>12131834
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

[Anonymous No.12131909]

>>12131882
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

[Anonymous No.12131914]

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

[Anonymous No.12131915]

>>12131610
Do you have to use Newtonian mechanics?

[Anonymous No.12131920]

>>12131914
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

[Anonymous No.12131935]

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

[Anonymous No.12131943]

>>12131935
What field?
Anyway, linear/abstract algebra

[Anonymous No.12131986]

>>12131935
Algebra
Get Pinter's book.

[Anonymous No.12132000]

>>12131935
Linear algebra and PDEs

[Anonymous No.12132048]

>>12131893
>>12131610
as always, you should check my work for yourself.

[Anonymous No.12132072]

>>12132048
These are the worst capital sigmas I've ever seen.

[Anonymous No.12132073]

>>12128061
How do we know Dedekind's construction of the reals is equivalent to Cantor's construction of the reals?

[Anonymous No.12132079]

>>12132073
>Dedekind's construction of the reals
https://www.youtube.com/watch?v=LSWIFXP2r14

[Anonymous No.12132080]

>>12131840
my calculator died so i had to do all the calculations by hand

[Anonymous No.12132106]

>>12132080
Did you do good?

[Anonymous No.12132125]

>>12132080
chad handman

[Anonymous No.12132136]

>>12132106

[Anonymous No.12132284]

>>12132072
I realized long ago I could never draw them quickly so I settled on something that I could do fast and was still unambiguous

[Anonymous No.12132329]

How did the dingos do it?

[Anonymous No.12132331]

>>12132048
Thanks and will do

[Anonymous No.12132364]

>>12128061
Brainlet question here
Can anyone explain me the answer? I don't get it

[Anonymous No.12132372]

>>12131720
>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:
https://www.sciencealert.com/astronomers-devise-a-way-to-test-predictions-of-a-pre-big-bang-universe
>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

[Anonymous No.12132401]

>>12132372
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"

[Anonymous No.12132442]

>>12132364
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

[Anonymous No.12132620]

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

[Anonymous No.12132814]

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?

[Anonymous No.12132932]

>>12132814
I do all my work in ms paint I don't even use pen and paper now.

[Anonymous No.12132981]

>>12132932
You use Paint like you use pen and paper tho, the process is the same.

[Anonymous No.12133037]

>>12132814
>How do I cope?
easy, neuralink is never going to work, no one is actually going to get to use it.
next

[Anonymous No.12133038]

>>12128061
Test

[Anonymous No.12133108]

>>12133038
Based.

[Anonymous 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.

[Anonymous No.12133139]

>>12133037
That's fair, thanks.
Also, thanks for the offer, but I don't really have any other questions.

[Anonymous No.12133188]

>>12132072
also, my writing on an ipad is dogshit. it's too slippery

[Anonymous 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.

[Anonymous No.12133395]

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.

[Anonymous No.12133402]

>>12133395
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

[Anonymous No.12133416]

>>12133402
>>12133395
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

[Anonymous No.12133454]

>>12133402
>>12133416
That was a very nice explanation anon. You're good at explaining things, I think that made it quite clear, thank you

[Anonymous No.12133462]

>>12133454
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.

[Anonymous No.12134204]

Slow thread, lads.

[Anonymous No.12134220]

>>12134204
there are No Questions, don't complain

[Anonymous 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

[Anonymous No.12134726]

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

[Anonymous No.12134827]

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?

[Anonymous No.12134843]

>>12134827
8/x+2/y=3
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

[Anonymous 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?

[Anonymous No.12134946]

>>12133315
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.

[Anonymous No.12135093]

>>12128454
and innumerable negative health problems

[Anonymous 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!

[Anonymous No.12135152]

>>12128454
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).

[Anonymous No.12135160]

>>12135093
genuine autism

[Anonymous No.12135174]

>>12134913
It's Bessel's correction, named after Friedrich Bessel.

[Anonymous No.12135185]

>>12135152
>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?

[Anonymous No.12135187]

>>12128335
>2020
>smoking
just dont, if you really want to get nicotine into your body smoking is literally worst way to do it

[Anonymous No.12135210]

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

[Anonymous No.12135376]

>>12135210
definition

[Anonymous No.12135575]

>>12135376
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.

[Anonymous 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?

[Anonymous No.12135639]

>>12135631
Forgot pic

[Anonymous No.12135648]

>>12135631
>>12135639
do you know any calculus? the easiest way is to find the zeros of the first derivative of f(x)

[Anonymous No.12135654]

>>12135639
Cosine is symmetric around any multiple of [math]2 \pi[/math]]

[Anonymous No.12135660]

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.

[Anonymous No.12135665]

Vent on me about your /sci/ frustrations

[Anonymous No.12135669]

>>12135654
*Any multiple of [math]\pi[/math] sorry

[Anonymous No.12135671]

>>12135660
https://en.wikipedia.org/wiki/Determinant

[Anonymous No.12135675]

>>12135665
My school is closed for the entire next week due to chink flu and it's driving me insane.

[Anonymous No.12135685]

>>12135675
what were you working on?

[Anonymous No.12135687]

>>12135685
CompSci.
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.

[Anonymous No.12135688]

>>12134204
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/?
>>12135575
Because autism.
>>12135665
I'm psychologically incapable of solving literally anything that comes out of the IMO or the Putnam.

[Anonymous No.12135701]

>>12135687
Why do you dislike working from home?
>>12135688
Have you tried any of the autistic studying methods like study groups?

[Anonymous 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.

[Anonymous No.12135715]

>>12135665
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 :)

[Anonymous No.12135718]

>>12135701
>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.

[Anonymous No.12135739]

>>12135715
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
>>12135718
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

[Anonymous No.12135740]

>>12135701
>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.
>>12135718
I'm like that too, so it's probably an autism thing.

[Anonymous No.12135748]

>>12135740
care, or else

[Anonymous No.12135763]

>>12135748
Or else what?

[Anonymous No.12136101]

>>12128061
does anyone know what this symbol in discrete logic?

[Anonymous No.12136107]

>>12136101
i am talking about the star thing never seen it before and Wikipedia doesn't seem to have it
https://en.wikipedia.org/wiki/List_of_logic_symbols

[Anonymous No.12136345]

>>12135660
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

[Anonymous No.12136447]

>>12135665
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.

[Anonymous 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?

[Anonymous No.12136928]

>>12135133
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.
>>12135575
Read more math, stop being a retarded faggot. It’s used constantly to define objects.
>>12135665
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.

[Anonymous No.12136948]

>>12131859
>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/.

[Anonymous No.12136962]

>>12136948
I don't know literally anything about electrical engineering.

[Anonymous No.12136979]

>>12136962
You literally do.

[Anonymous No.12137005]

>>12135133
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.

[Anonymous No.12137009]

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?

[Anonymous No.12137047]

>>12131639
>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.

[Anonymous 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

[Anonymous 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]?

[Anonymous No.12137245]

>>12137222
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]

[Anonymous No.12137250]

>>12137245
Thank you.

[Anonymous No.12137382]

>>12137129
>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.

[Anonymous No.12137434]

>>12137382
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

[Anonymous No.12137532]

>>>/pol/278127415
>even Tooker is in the RBG sticky
LMAO.

[29 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?

[Anonymous No.12137788]

>>12137784
>I have an IQ of 139
Stopped reading here.

[Anonymous 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).

[Anonymous 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

[Anonymous No.12138040]

>>12138022
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.

[Anonymous 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"?

[Anonymous No.12138481]

>>12137005
Cheers anon, that was short and to the point.

[Anonymous No.12138526]

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

[Anonymous No.12138642]

>>12138526
nvm, im an idiot

[Anonymous No.12138790]

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

[Anonymous 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.

[Anonymous No.12138854]

>>>/wsr/891507

[Anonymous No.12139315]

>>12137943
bump

[Anonymous No.12139319]

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

[Anonymous No.12139553]

>>12139319
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.

[Anonymous No.12139640]

redpill me on pendulums

[Anonymous No.12139698]

>>12139640
What do you want to know

[Anonymous No.12139789]

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]

[Anonymous No.12139830]

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]?

[Anonymous No.12139966]

>>12139640
When dealing with chaotic systems, small angle approximation doesn't work anymore.
Is that redpilled enough?

[Anonymous No.12139976]

>>12136948
Whatever happened to Yukarifag? God I miss that faggot...

[Anonymous No.12139997]

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

[Anonymous No.12140004]

>>12139997
achilles and the tortoise?

[Anonymous No.12140008]

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

[Anonymous No.12140109]

>>12139997
Zeno's paradox

[Anonymous No.12140130]

>>12139976
They bullied him off the board, this used to happen to anyone annoying on any board before the reddit colonization.

[Anonymous No.12140140]

>>12139976
Conjecture one:
He got bored and fucked off.
Conjecture two:
Whenever he thinks about /sqt/ he recalls this >>/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.

[Anonymous 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!

[Anonymous No.12140324]

>>12140140
>>>/sci/thread/S11475807#p11484606
Who was in the wrong here?

[Anonymous No.12140371]

>>12140140
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!

[Anonymous No.12140383]

>>12140371
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.

[Anonymous No.12140385]

>>12140249
>what causes seasonal depression
being sad
>how do i mitigate it
be happy instead

[Anonymous No.12140401]

>>12140371
the need for social validation is more fundamental than the instinct towards higher reason. even autistic homosexual geometers cannot resist

[Anonymous No.12140407]

>>12140324
This >>/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.
>>12140371
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+

[Anonymous No.12140479]

>>12140407
Thoughts on Patchouli Knowledge?

[Anonymous No.12140519]

>>12140407
Keep posting remilia bro, I love her and I love you

[Anonymous No.12140557]

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

[Anonymous No.12140561]

>>12140557
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

[Anonymous No.12140573]

>>12140561
I'm assuming f is the frictional force so the inclined plane assumption is probably corect.

[Anonymous No.12140576]

>>12140561
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.

[Anonymous No.12140596]

>>12140576
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.

[Anonymous No.12140611]

>>12140596
That makes sense.
Thanks.

[Anonymous 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?

[Anonymous No.12140716]

>>12140696
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].

[Anonymous No.12140721]

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

[Anonymous No.12140728]

>>12140721
avatarfagging is against the global rules.

[Anonymous No.12140733]

>>12140728
lol

[Anonymous No.12140738]

>>12140728
If only.

[Anonymous No.12140801]

>>12140407
>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.

[Anonymous No.12140814]

>>12140733
>>12140801
it is explicitly prohibited per the global rules.

[Anonymous No.12140816]

>>12140814
so are half the threads on this godforsaken board. does that mean anything?

[Anonymous No.12140828]

>>12140814
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

[Anonymous No.12140911]

>>12128061
So I'm back at school and taking calc 2, but I ran into a problem I've had trouble solving.

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

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

?

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.

[Anonymous No.12141092]

>>12140911
i think you may have copied the problem down incorrectly

[Anonymous No.12141109]

>>12141092

[Anonymous No.12141159]

>>12141109
yep just sub u = 2x
you can then replace f(u)du with f(x)dx

[Anonymous No.12141214]

How do ants solve the trolley problem?

[Anonymous No.12141223]

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).

[Anonymous No.12141246]

>>12141223
Lemma?

[Anonymous No.12141252]

>>12140828
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.
>>12140816
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.

[Anonymous No.12141254]

>>12141159
thank you fren

[Anonymous No.12141257]

>>12141223
Theorem: Conjecture is true/Conjecture is false.
Proof: The proof goes here.

[Anonymous No.12141276]

>>12141252
It's not that big of a deal, bro.

[Anonymous No.12142051]

>>12140479
Patcho is cute.
>>12140721
Note taken.
>>12140801
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.

[Anonymous No.12142181]

>>12142051
>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.

[Anonymous 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.

[Anonymous 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?

[Anonymous No.12142285]

>>12142280
the object is traveling 1 km/s in its own frame of reference *

[Anonymous No.12142291]

>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

[Anonymous No.12142315]

>>12142280
The reception period would be almost indistinguishable from the emission period, because [math]\frac{v}{c} << 1[/math].

[Anonymous No.12142317]

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?

[Anonymous No.12142323]

>>12142315
would the period be larger or smaller than 1 second

[Anonymous No.12142338]

>>12142323
Very slightly larger.
[eqn]f_{rec} = \sqrt{\frac{1-\beta}{1+\beta}}f_{em}[/eqn]
with [math]\beta = \frac{v}{c}[/math]

[Anonymous No.12142363]

>>12142323
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?

[Anonymous No.12142410]

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.

[Anonymous No.12142441]

>>12128104
>>12119726

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.

[Anonymous No.12142459]

>>12142410
>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.

[Anonymous No.12142486]

>>12142317
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?

[Anonymous No.12142491]

>>12142486
I can't just google, no. I need to calculate [math] n [/math] required by using the given bounds.

[Anonymous No.12142541]

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')...

[Anonymous No.12142619]

>>12140140
>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.

[Anonymous No.12142643]

>>12142541
[math]y+y'=1[/math], same way they knocked out the [math]x+x'[/math] term in the previous step

[Anonymous No.12142652]

>>12142643
sorry i don't know anything about anime. isn't this yukari? so yukari is back?

[Anonymous No.12142655]

>>12142652
no thats not yukari

[Anonymous No.12142676]

>>12142652
Are you aware of what Google is?

[Anonymous No.12142750]

>>12142459
Ah christ of course, thanks. I knew it had to be something simple

[Anonymous No.12142791]

>>12142676
and how is that different? same color palette of pinkish colors, same everything.

[Anonymous No.12142793]

>>12142676
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.

[Anonymous No.12142831]

>>12142791
you mind rereading that and posting something else? the green dressed, blond haired girl isnt pinkish

[Anonymous 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?

[Anonymous 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?

[Anonymous No.12142954]

>>12142946
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

[Anonymous No.12142964]

>>12142946
>'there exists' should be a subset of 'for all'
It shouldn't.

[Anonymous No.12142967]

>>12142954
idgi
what do you mean by 1=x=0?

[Anonymous No.12142983]

>>12142946
consider the case where [math]A={ }[/math]

[Anonymous No.12142987]

>>12142967
1=x AND x=0

[Anonymous No.12143001]

>>12142999
new thread

[Anonymous No.12143949]

>>12142363
no one?