/sqt/ /qtddtot/ - stupid questions thread

[Anonymous No.12103457]

FULLY DESCRIBING YOUR PROBLEM EDITION. ONLY POST HERE IF YOUR QUESTION IS ENTIRELY UNAMBIGUOUS.

The thread for questions that don't deserve their own thread
For book recommendations, check the sticky and/or the /sci/ wiki.
To download free books, search for libgen or scihub
For learning how to use the inboard latex, check the sticky. You can also test your latex before you post by clicking the "TEX" button in your reply box. Feel free to test in this thread, but delete your post afterwards.

If you ask any question, remember that there is almost no universal notation in many fields.
>What is a BAD question?
Help me with this problem.
Do this problem for me.
What does T mean in this equation: μχ=33Tℵ
>What is a GOOD question?
Here's the problem I'm having trouble with. I've tried ____, but it didn't work. I don't know how to get past _____.
>generic example of person who explains the notation of their problem or the variables included in their image

unanswered questions from last thread and their complexities:
>>12093131 (off-topic, unanswerable)
>>12093349 (organic chemistry, difficult)
>>12093407 (mathematics, untraceable)
>>12094680 (medicine, probably easy idk lol)
>>12095136 (off-topic, not worth it)
>>12099911 (computer science, buttplug-tier)
>>12102720 (chem/biochem, medium-rare)
most everything was answered good job bros

last thread >>12093089

[Anonymous No.12103510]

since I've made the last 3 threads, any suggestions to the OP would be appreciated
>no uni advice
I won't add that, I know it's helpful to some people and this is the best place for it on this godforsaken board

[Anonymous No.12103687]

>>12103510
bumps

[Anonymous No.12103698]

explaing why i need to learn about quantum mechanics as a comp sci major (130 IQ tested)

[Anonymous No.12103717]

>>12103698
you don't, unless you go to caltech. don't they make every science major take QM?

[Anonymous No.12103726]

>>12103510
add the suggestion to look on google scholar for answers to questions, use the wiki for textbooks (provide them with a wiki link), use libgen for textbooks (don't link this), suggest sci-hub for papers (you can link this I believe), direct /g/, /diy/, and /adv/ questions to their respective boards, this isn't a dumping ground for other boards incompetence to come to fruition. remember no bullying in /sqt/ and no cheating on exams. link to the book charts, you should be able to find them through the mega file link that the older (based) autist used to include in the OP. Get rid of the example of a good or bad question, not only is it pretentious and intimidating but people will ignore it. Try to group the types of unanswered questions together more efficeintly. Don't comment on the quality of questions that are unanswered if you have no idea what you're talking about. Continue linking to the old threads.

[Anonymous No.12103736]

>>12103717
im taking chem 1 lab as a junior at harvard and we are literally talking about the double split experiment and heisenberg shit already and calculating probability density plots

[Anonymous No.12103750]

>>12103726
noted, but the question example is important because people don't understand what bad notation looks like. I don't have the old OP textbook list, and I feel like organizing old unanswered questions by field doesn't matter when there's only 7 of them. I said nothing about their qualities btw.
>>12103736
okay what does this have to do with anything? you already know the answer. you're learning """quantum mechanics""" as an example for a project, not as a subject.

[Anonymous No.12103763]

>>12103750
you sound jealous

[Anonymous No.12103771]

>>12103763
jealous of what?

[Anonymous No.12103775]

>>12103750
>I don't have the old textbook lists

Go here:

>>/sci/

and do a search for /sqt/ the textbook charts are listed.

The sci wiki page is here:

https://4chan-science.fandom.com/wiki//sci/_Wiki

Google scholar is here:

https://scholar.google.com/

sci-hub.tw (there are other links)

Group the questions together, it is custom to do so. Don't comment on any questions if you don't understand what is being asked, it is confusing.

[Anonymous No.12104022]

>>12093349
>How do i draw this??
literally google "figlu structure"
form = 1 carbon, like formic acid
imino = C=N bond

[Anonymous No.12104157]

I'm asked to find the Y Matrice of this network.
I have the solution, but I'm not sure how they arrive at the answer.
Y21 = -1/(Zb)
Y11 = ((YaYb)/(Ya+Yb))^-1
I know I'm supposed to open the circuit at port 2, but from there I'm confused how they get this answer.

[Anonymous No.12104249]

>>12099911
>Can I just put my project on github and not worry about backups?
Yes
>Is there any advise to someone starting to do computational physics?
Unless you want to build everything from the ground up as an excercise, you can just try out openfoam and see how it does things.

[Anonymous No.12104356]

Say that there's a 2D creature and its world is a paper, what'd it see at the edge of said paper? Could it be the same as how us see the black hole as in it looks like a void because our mind can't comprehend higher dimension?

[Anonymous No.12104367]

What's an employable degree for stupid aspies? Europe so CS flies out the window, low social ability so Business stuff does too, and also too stupid for big brain things like Physics and Math. Oh well, everything seems bad.

[Anonymous No.12104393]

For [math]\{B_i\}_{i\in I}[/math] an arbitrary family of sets, if I fix a field (or ring) and interpret each [math]B_i[/math] as a basis that generates the vector space (or module) [math]V_i[/math], then my intuition is that:
>The direct sum [math]\bigoplus_{i\in I} V_i[/math] is generated by the disjoint union of the [math]B_i[/math]'s
>The direct product [math]\bigotimes_{i\in I} V_i[/math] is generated by the Cartesian product of the [math]B_i[/math]'s (assuming axiom of choice)
Is this right?

[Anonymous No.12104438]

>>12104367
Just go for CS and if you can't work outside Europe just hope someone would hire you to work remotely

[Anonymous No.12104473]

>>12104157
I get:
y11=y22=Ya(Ya+Yb)/(2Ya+Yb)
y12=y21=-Ya^2/(2Ya+Yb)

[Anonymous No.12104497]

Why did Kant think math was a synthetic enterprise? Why isn’t the complete concept of “12” contained within the phrase “7+5”?
Basically: how couldn’t math be analytic?

[Anonymous No.12104508]

>>12104497
What are the definitions there, Kant was on some abstract outside the box philosophy. Math in itself is analytic. Bit it relies on faith in your axioms which can't be proven I guess.

[Anonymous No.12104533]

>>12104508
Very simply: an analytic statement is a sentence in which the predicate is contained within the subject. “A bachelor is an unmarried man.” It’s basically a definition. Assuming that a synthetic statement is possible, it would be a sentence in which the predicate builds on the subject. “The cat is 15 pounds.” That’s an example of an a posteriori synthetic statement. Kant says that math is done in a priori synthetic statements and I don’t understand how he can think that at all.

[Anonymous No.12104618]

can someone please explain to me how this
[math]\frac{x^2-4x+3}{x^4-4x^3+6x^2-4x+1}[/math]
is simplified into this?
[math]\frac{x-3}{(x-1)^{3}}[/math]

[Anonymous No.12104624]

>>12104618
The denominator is [math](x-1)^4[/math] expanded, which you can tell by recognizing the 5th row of the Pascal triangle (leading coef. is positive and the coefficients alternate in sign).
The numerator is a quadratic where the roots are 1 and 3, thus can be written as [math](x-1)(x-3)[/math].
Hence the result.

[Anonymous No.12104632]

Linking from previous thread
>>12104628
Am I a retard?

[Anonymous No.12104636]

>>12104618
Factor the numerator and then think about what happens if you take the fourth power of one of the factors. If you can’t see where this is coming from look up pascal’s triangle. If you want to waste more of your time look up polynomial long division. Ask this in /sqt/ next time.

[Anonymous No.12104653]

>>12104632
Either that or 42%*1.2=50.4%, depending on how retarded the person who made the question is

[Anonymous No.12104662]

>>12104624
thanks

[Anonymous No.12104663]

>>12104653
Multiply by 1.2

It’s a very clear problem, the wording is only ambiguous because of the idiotic contrived storytelling and the unnecessary use of percentages. They’re just asking what is 1.2 times an outreach of .42

[Anonymous No.12104674]

>>12104632
>numerical reasoning test
>actually tests whether you're from the same culture as the test writer

[Anonymous No.12104742]

Damn, not only was mine not answered but I couldn’t even make the unanswered list...anyway, reposting this >>12096143

[Anonymous No.12104754]

Does this check out? Fairly simple just thought among human energy consumption
If electricity is 0.17USD/kwh
8700kj/day energy use
Then @ 1kw charge rate
8700000j÷1000(j/s)
8700s/(60^2)
2.42*.17
=0.41USD
?
So humans would only cost 41 cents per day to run on electricity ?

[Anonymous No.12104778]

>>12104742
The voltage won't float, provided that the neutral connection remains intact. If the external neutral connection breaks but you've removed the local grounding rod (while leaving the earth line connected to neutral), any grounded conductor (e.g. most metal chassis) will become live.

[Anonymous No.12105006]

can someone please help me with this-
>"between all the isosceles triangles with a perimeter of 24cm what's the base of the triangle with the largest area"

what i've been doing is [math]base=x[/math] and [math]sides=\frac{24-x}{2}[/math]
then finding height-
[math]height^2+0.5x^2=(\frac{24-x}{2})^2[/math]
[math]height=\sqrt{\frac{(24-x)^2}{4}-0.5x^2}[/math]
and then creating equation-
[math]f(x)=\frac{x*\sqrt{\frac{(24-x)^2}{4}-0.5x^2}}{2}[/math]
is this correct? and if it is then how to i calculate the derivative? because if this is right it means i'm messing up the derivative

[Anonymous No.12105009]

>>12104653
I thought so. thanks.

>>12104663
The wording is ambiguous regardless of context.
If you went out to buy a house for $100,000 , and the realtor asked you for a 20% deposit, you would pay $20,000.
Then they call you next week and say they need 5% more.
Do you (i) send them 5% of $20,000 more ($1,000), or (ii) send then 5% of $100,000 more ($5,000).
(i) represents 5% larger (the deposit need to be 5% larger than it is now)
(ii) represents 5% more (the deposit needs to represent 5% more of the original number)

So by that logic, 20% more outreach is original outreach + 20% of base (i.e. 62%).

[Anonymous No.12105020]

>>12105006
You have to square 0.5
derivative is product rule and chain rule

[Anonymous No.12105052]

>>12105020
>You have to square 0.5
fuck i always make such stupid mistakes
thank you

[Anonymous No.12105216]

Okay physics bros, here is something that has been bothering me since I ever heard of it, time-reversal symmetry.
The quick wiki definition: "the theoretical symmetry of physical laws under the transformation of time reversal".
Say I throw a ball (or a particle travels through some medium), if time is reversed mid-throw, the ball should return to me, or the particle instantly reverses its trajectory. Is this what it means?
What then when I have thrown the ball and it is at rest, what does sudden time-reversal do? The ball should not spontaneously jump back to me. A symmetrical reversal of physical laws should not provide new energy to the ball nor take energy away from the ball.
Am I too much of a brainlet here?

[Anonymous No.12105397]

>>12105216
Don't think about it too hard.
If the variable is proportional to t^2n it's symmetric under time reversal, if it's proportional to t^(2n+1) it's not.
That's simply because (-t)^2=t^2
So v changes direction, x doesn't.
>A symmetrical reversal of physical laws should not provide new energy to the ball nor take energy away from the ball.
It doesn't. When the ball hit the ground it lost energy. If you reverse time it gets the energy back.

[Anonymous No.12105412]

how do i find the energy needed to free an electron? i know that the goal is to go from the lowest energy level of an atom to energy level 0 but it's illegal to divide by zero

[Anonymous No.12105416]

>>12105397
I'm okay with accepting that.

>When the ball hit the ground it lost energy. If you reverse time it gets the energy back.
But how... assume the energy is dissipated as heat, why would the energy flow back into the ball and not anywhere else?

I can accept the proposition, similar to how I can learn to accept many of the theories of QM, but it appears just as weird to me, perhaps even weirder now than when I learnt of it initially.

[Anonymous No.12105432]

>>12105412
It depends on what the electron is bound to or what atom shell it is located in. An electron in some bulk material will have a specific energy associated with the atomic composition and shell structure of the material.

[Anonymous No.12105443]

>>12104778
Why would the neutral stop the voltage from floating? It’s just the return right? If you remove the ground connection (at the transformer or wherever else) then how would it still be referenced to ground? Or do the powerlines themselves determine what voltage you get from the transformer (given a fixed turn ratio) since they’re (I believe) not floating? But in that case the neutral isn’t involved.

[Anonymous No.12105447]

>>12105416
>assume the energy is dissipated as heat
Then it's not symmetrical anymore

[Anonymous No.12105448]

>>12105432
let's start easy and say it's a hydrogen atom in a not excited state

[Anonymous No.12105463]

>>12105448
Integral of potential energy from it's state to infinity

[Anonymous No.12105465]

>>12105447
Thanks, actually that clears it up.

[Anonymous No.12105598]

>>12105412
in a solid this is referred to the "work function"
in an atom this is referred to as "ionization energy." it is only exactly calculable for certain simple systems.

if you're working with just hydrogen and I understand your level of background correctly, you can take your function that gives you the wavelength of light when an atom transitions between two atomic levels [eqn] \frac{1}{ \lambda} = R_H( \frac{1}{n_1^2} - \frac{1}{n_2^2} ) [/eqn] and plug in n1=1, n2=infinity (which reduces the fraction to 0)

you were confused since you don't want "Energy level 0" which isn't possible, there's a ground state of energy level 1. The unbound electron is at "level infinity"

[Anonymous No.12105622]

>>12105598
forgot to mention, once you have the wavelength then calculate the energy of a photon with this wavelength

[Anonymous No.12105645]

>>12103750
>I don't have the old OP textbook list
Just this once.

>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.lc (warn me if the link breaks)
https://stitz-zeager.com/
>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://imgur.com/a/HNETQCb
>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
>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
Related meme image that you can use to insult people: https://imgur.com/a/BGLrDX1

Stuff:
Meme charts:https://imgur.com/a/JY6NNeL
Serious charts: https://imgur.com/a/0qDEgYt (Post any that I've missed.)
Verbitsky: 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/

Check out the Latex thing btw. I'm not posting but I'll still read the feedback.

[Anonymous No.12105773]

>>12105645
cheers, I'll integrate almost all of this I think.

[Anonymous No.12105940]

>>12105443
>Why would the neutral stop the voltage from floating? It’s just the return right?
The neutral is usually grounded at the transformer as well as at the premises. The grid neutral is grounded by virtue of the neutral wire being bolted directly to the pylon (rather than to an insulator). Even if it isn't grounded at the transformer, if you share a connection with other properties (i.e. you don't have your own transformer), neutral will be grounded at each property.

At least, that's the case in the UK (3-phase star/wye, TN-C-S grounding); it might be different in the US.

[Anonymous No.12105941]

In quantum mechanics is it possible to model the probability of spin +1 without complex numbers? I'm talking about a simple qubit system where you measure the spin and rotate your measurement device in a 3D plane.

I just don't see the need for a Hilbert space here. At what point do complex numbers become necessary?

[Anonymous No.12105945]

>>12103457
I have problems understanding trigonometry, vectors, imaginary numbers, functions, integral and differential stuff. And I have a problem with calculating stuff in my head due to low RAM in there.
Some of the things I used 6 years ago in school, some I never heard of but I should understand everything within the next 1-2 weeks for uni (IT related).
How fucked am I/ how can I study this stuff efficiently? What are efficient courses? I don't mind studying a lot, just don't wanna waste tons of time doing it.

[Anonymous No.12105964]

>>12105941
do you mean spin-1/2?
look up the bloch sphere

[Anonymous No.12105974]

>>12105773
you should just copy that and remove your version since it’s inferior

[Anonymous No.12105976]

>>12105941
>I just don't see the need for a Hilbert space here
This has nothing to do with complex numbers.
>At what point do complex numbers become necessary?
complex numbers are just efficient ways to describe rotation. It should be possible to use matrizes instead.

[Anonymous No.12105980]

>>12105974
And you should be grateful that anyone's making it in the first place

[Anonymous No.12105997]

>>12105964
>>12105976
A qubit has spin +1 or -1. If you measure +1 and rotate the device 180 degrees you'll get -1 on your next measurement. If you rotate it 90 degrees it's +/- 1 with probably 0.5. The expected value can be modeled by cos x where x is the degrees of rotation.

Can this be extended to 3d space by just having 3 axes?

[Anonymous No.12106000]

>>12105997
this is a spin-1/2 system friend. there are 2 spin states.
look up the bloch sphere like I said

[Anonymous No.12106002]

>>12106000
A bloch sphere is exactly what I posted above.... my question is why complex numbers make it easier, why not just use a 3d cartesian space?

[Anonymous No.12106006]

>>12105997
CSnigger

[Anonymous No.12106008]

>>12106002
Because you need two components for each dimension, so 6d

[Anonymous No.12106011]

What happens if one hits an atom core with really high power laser?
Does it vaporize?
Does it explode?

[Anonymous No.12106012]

>>12106011
yes

[Anonymous No.12106013]

>>12106012
yes what

[Anonymous No.12106015]

Are continuous partials required for a complex valued function to be analytic in some [math]D \subseteq \mathbb{C}[/math]?

[Anonymous No.12106017]

>>12106002
how do I expect you to know that you posted a bloch sphere when you don't know that +/-1 spin states is a spin-1/2 system?

[Anonymous No.12106021]

anyone familiar with mach reflections?
I have no idea how to even start the highlighted part

[Anonymous No.12106022]

>>12106011
high power doesn't mean anything unless it's the right wavelength. if it's a long wavelength it'll polarize the atom core but not do anything to it

[Anonymous No.12106024]

>>12106013
yes yes

[Anonymous No.12106030]

>>12106022
interesting
can you explain why?

[Anonymous No.12106033]

>>12106008
up, down, left, right, forwards, backwards... there are 6 components. not being retarded i'm just learning this for the first time and I'm finding it difficult to see why you can't model this system in normal 3d space.

[Anonymous No.12106034]

>>12106024
This.

[Anonymous No.12106041]

>>12106030
in general, EM waves don't affect anything that's "smaller than their wavelength." You'll never ionize an atom by sending microwaves at it, no matter how intense the waves are. What matters is the energy of the wave, which corresponds to the (inverse of the) wavelength. Smaller wavelengths->higher energy->can affect more things.

if you have a big water wave, it'll push a boat but not destroy it. if you have a really concentrated wave that hits the side of the boat it can pierce it.

[Anonymous No.12106044]

>>12106033
I don't understand because you posted the bloch sphere. in it you encode the spin information in 3D. what's wrong with this?

[Anonymous No.12106045]

>>12106021
like seriously Im fucking begging I am in distress

[Anonymous No.12106050]

>>12106041
alright got it
thanks

[Anonymous No.12106061]

>>12106044
Okay sorry forget what I said. QM uses complex numbers, conjugates, vector spaces, hermitians etc.

why can't we use a model with real entities only?

[Anonymous No.12106107]

>>12106061
We can. Just replace each complex number with a two dimensional vector. Then rotate it.

[Anonymous No.12106115]

Will this fix my brain?

[Anonymous No.12106151]

>>12106115
Yes.

[Anonymous No.12106203]

>>12106151
Do you say that confidently?

[Anonymous No.12106228]

can anyone tell the fuck is wrong with my solution?
[math]\int \frac{1}{\sqrt {x^3}} dx =
\int x^-\frac{3}{2} dx =
- 2x^-\frac{1}{2} + C =
- \frac{2}{\sqrt {x}}
[/math]

Wolfram integrates it by parts, so I can't tell where I messed up

[Anonymous No.12106235]

>>12106228
these fractions are all meant to be exponents btw, I can't into latex sry

[Anonymous No.12106239]

>>12106228
I think you just plugged it in wrong because this is correct

[Anonymous No.12106265]

>>12106239
yeah I just didn't notice it at first because wolfram didn't simplify it and I it didn't occur me to do so. thanks a bunch, I just got back to uni because of the whole covid thing so I'm more than rusty, and sorry for taking your time lol

[Anonymous No.12106283]

>>12106203
Yes.

[Anonymous No.12106465]

>>12106235
>I can't into latex sry

If it's more than one character, you need to put your exponents inside curly brackets. Pic related is the /sci/ intro guide to LaTeX

[Anonymous No.12106629]

>>12103457
I read a paper that stated "the fluorophore has very low fluorescence in an aqueous solution" but im having trouble trying to understand that. By very low fluorescence do they mean that the brightness is supposed to be very low? And if so would a low brightness correlate to a small stokes shift or a large stokes shift?

[Anonymous No.12106859]

Why is time linear? By linearity I mean the distance between each minute in an hour, each hour in a day, each day in year etc. Why can't even one of these units of time be non linear?

[Anonymous No.12106944]

>>12106045
>>12106021
it's over...

[Anonymous No.12106967]

>>12106859
we wouldn't know

[Anonymous No.12107107]

Why is it that tinted windows cannot be seen through in the day, but at nighttime if there is a light source inside the room with tinted windows, we can see through it clearly regardless of tint?

[Anonymous No.12107215]

Why do some people eat a lot of junk food and never work out and don't gain weight? And some people do work out and yet they balloon uncontrollably (for example some professional tennis players look pretty fat)

[Anonymous No.12107297]

>>12107215
High metabolism rates can play a role.

[Anonymous No.12107298]

Can someone help me with part c.) here? How can I check independence if I do not know the probabilities of [math] P(X=1,Y=0), P(X=0,Y=1),P(X=0,Y=0)[/math]? Two rv are independent if [math]P(X \in A, Y \in B)= P(X \in A)P(Y \in B)[/math] so I am not sure how to check this condition

[Anonymous No.12107312]

>>12107298
kill yourself

[Anonymous No.12107315]

>>12107215
>Why do some people eat a lot of junk food and never work out and don't gain weight?

The calorific content of the food you eat determines whether you lose/gain weight, regardless of whether or not it's junk. Dr Mark Haub lost weight on a "convenience store" diet consisting of stuff like Twinkies and Doritos: https://www.npr.org/2010/11/12/131286626/professor-s-weight-loss-secret-junk-food?t=1599794307393.. Such a diet is of course extremely unhealthy, but eating junk food won't make you fat as long as you control the calories.

[Anonymous No.12107325]

>>12107312
i will after if you help me you fucking faggot

[Anonymous No.12107359]

How do i determine the density of a liquid using its upthrust?

[Anonymous No.12107363]

How do I show this? I feel like I'm close using the hint. Picture of my work in a second

>>12107107
It's a question of whether the majority of the light is coming from through the glass or reflected off the glass on your side. When you're on the brighter side of the glass, the image coming through the glass is drowned out by reflected light on your side. When you're on the dark side, there's relatively more light coming through the glass and you can see through it.

[Anonymous No.12107371]

>>12107363
My attempt. I figure $a$ should be real, so the discriminant should be positive. But that gives me the opposite of what I'm trying to prove. One of my classmates set the discriminant to be negative and said something about a midpoint, but I have no idea why, or why he's ok with $a$ being complex when it takes the hint outside of its supports.

This is probability theory, by the way

[Anonymous No.12107388]

>>12107312
This.

[Anonymous No.12107396]

>>12107298
did you do part b? that will give you probabilities p and q. what are these values?

[Anonymous No.12107410]

>>12107371
Got it. This is pretty abstract to me
https://www.purplemath.com/modules/ineqquad2.htm

[Anonymous No.12107425]

>>12107363
thanks good explanation

[Anonymous No.12107464]

>>12107425
Cheers, lad.

[Anonymous No.12107493]

>>12107410

Your working is correct, but you've got the inequality backwards in [math](85)[/math] and [math](86)[/math]

[Anonymous No.12107499]

>>12103457
How can I improve my latex live preview compilation script? It works fine for my undergrad stuff but It could probably be improved. I use zathura to view pdfs cause there it's the least obnoxious when it refreshes.


1 #!/bin/bash
2
3
4 while :
5 do
6 if [ $1 == '-bib' ]
7 then
8 lualatex -interaction nonstopmode $2 > /dev/null
9 bibtex $2
10 lualatex -interaction nonstopmode $2 > /dev/null
11
12 else
13 lualatex -interaction nonstopmode $1 > /dev/null
14 fi
15
16 rm *.out
17 rm *.aux
18 rm *.dvi
19 rm *.log
20
21 sleep 1
22
23 done

[Anonymous No.12107503]

>>12107499
Here is it not retardedly copy and pasted from vim.
https://gist.github.com/Fitzy1293/b370d63a5c919d1c990fca42f3c8a717

[Anonymous No.12107508]

>>12107499
you wrote a script to preview your tex as you're typing it? you can't be bothered to hit the recompile key?

[Anonymous No.12107511]

>>12107508
>you can't be bothered to hit the recompile key?
No

[Anonymous No.12107623]

>>12107511
why don't you just make a script that hits the recompile key every 30 seconds lmao

[Anonymous No.12107638]

>>12107493
Good catch, thanks

>>12107371
>>12107410
Now how about this one? I've been trying to do it by pointing out that the correlation coefficient is +/-1, and that I can calculate that by using the desired equality without substituting X=cY. But I can't seem to progress, and I'm worried it's because this approach is no good.

[Anonymous No.12107639]

Still trying to show the equality on line 97 and I don't see any way to simplify things

[Anonymous No.12107649]

>>12107623
That's basically what the script does.
I don't use the miktex editor because I like to use the same text editor for everything. And miktex and similar editors are bloated beyond belief.
Often I'll have to open some random .csv or code or something and it's nice to do it in one place.
The script just runs in the background and whenever I save it updates the pdf. It's pretty nice to do it like this.

[Anonymous No.12107681]

Due of the uncertainty principle, would it be impossible to ever know the location of a photon (because the speed of light is a constant, so you should always know the momentum)?

[Anonymous No.12107684]

>>12107681
you can measure the position of a photon via detection, but this kills the photon and removes all of its momentum
there's no non-destructive method to measure the position (to my knowledge)

[Anonymous No.12107758]

What do ppl mean by render in mandlebrot? When people make animation from mandlebrot is it from one formula or multiple?

[Anonymous No.12107819]

>>12107681
Photons momentum isnt related to its speed

[Anonymous No.12107840]

>>12107758
What do you mean?
When you solve the equation at 0,0.5,1 and you zoom in on 0,0.5 you have to calculate 0.25 to maintain the resolution. That's what is being rendered

[Anonymous No.12107858]

>>12107681
in 'perfect' conditions it is constant, measuring it will create 'imperfect' conditions which could affect its velocity and/or trajectory
>>12107819
yes it is

[Summer<3 !A4jsQTgi.Q No.12107866]

https://youtu.be/V-FCjmxE3QE

what're some other interesting consumer medical technology machines?

[Anonymous No.12107918]

>>12107858
>yes it is
You know what I mean

[Anonymous No.12108113]

>>12107363
I think you're overdoing it.
[math]E((X+aY)^2) \geq 0[/math] necessarily implies [math]\Delta = 4(E(XY))^2-4E(X^2)E(Y^2) \leq 0[/math].

[Anonymous No.12108183]

>>12107359
The upward force on a submerged object is equal to the weight of the equivalent volume of liquid minus the weight of the object. So if the object has mass M and volume V, the liquid has density ρ, and gravitational acceleration is g, the force is F=g(ρV-M)=ρgV-gM => ρ=(F+gM)/gV=(F/g+M)/V.

If the object is only partially submerged, then V is the volume of the submerged portion. A hydrometer measures density by measuring the submerged volume when F=0 => ρgV-gM => V=M/ρ => ρ=M/V.

[Anonymous No.12108216]

>>12107396
[math]p=1/(3q)[/math]

Still not sure how that helps since I don't know what the other values are.

[Anonymous No.12108217]

>Advanced Thermo Cycles, and
>CFD
or
>Manufacturing Systems, and
>FE Techniques

Both sets of modules are interesting but I'm not sure what to pic.
One focuses on manufacturing and the other on Thermodynamics
Any help, or experiences?

[Anonymous No.12108264]

>>12103457
how do i get only x on the left hand side:

x * b / (a + x) = w

[Anonymous No.12108271]

>>12107493
>>12107623
>>12107638
>>12107639
>>12108113
>>12108183
>>12108216
please answer me.

>>12108264

[Anonymous No.12108345]

>>12108264
>>12108271
/sci/ is a pretty slow board, try not to be so impatient. That said, you can do the following;

-divide by b
-multiply through by the denominator
-move the x term on the right-hand side to the left-hand side
-factor out x on the left-hand side
-divide through to get x on its own

[Anonymous No.12108354]

>>12108216
>>12107298
bumping for help pls

[Anonymous No.12108473]

>>12108354
Hint: P(X=1, Y=0) = P(X=1) - P(X=1, Y=1).

[Anonymous No.12108474]

>>12108354
Correlation is just covariance divided by the product of standard deviations. So the correlation is zero when the covariance is zero.

More generally, you have 4 probabilities for the 4 possible combinations of X and Y. You know that:
1. P(0,0)+P(1,0)+P(0,1)+P(1,1)=1
2. P(1,1)=1/3
3. P(1,0)+P(1,1)=p
4. P(0,1)+P(1,1)=q
So given p and q, you can work out the probabilities of the 4 distinct cases:
P(0,0)=4/3-p-q
P(1,0)=p-1/3
P(0,1)=q-1/3
P(1,1)=1/3
From that, you can work out the covariance, which is 1/3-pq. This is zero (and thus so is the correlation) when pq=1/3 <=> p=1/3q <=> q=1/3p.

X and Y are independent if P(0,0)/P(1,0) = P(0,1)/P(1,1) (i.e. P(X=0)/P(X=1) is the same whether Y=0 or Y=1) and vice versa
=> P(0,0)*P(1,1)=P(0,1)*P(1,0)
=> (4/3-p-q)*(1/3) = (p-1/3)*(q-1/3)
=> 4/9-p/3-q/3 = pq-p/3-q/3+1/9
=> 4/9 = pq+1/9
=> pq=1/3
which is the same constraint as for uncorrelation. IOW, if they're uncorrelated then they're independent.

[Anonymous No.12108666]

Why is Internal Energy only a function of temperature in case of ideal gases?

[Anonymous No.12108691]

Physicsfag here with a math question. I want to solve Schrödinger's equation in a box [0,1] with a sloped potential, i.e. V(x) = c x. The solutions are Airy's equations. I take a linear combination that satisfies the boundary conditions (the function is zero at the ends) and the energy is quantized as a result. This final set of wave functions should be orthogonal due to Sturm–Liouville. Is there any way to neatly represent them? Have their properties been studied?

In other words: solutions to SL are often nice. How nice are they when restricted to a finite domain?

[Anonymous No.12108824]

>>12108691
Like this?
https://arxiv.org/ftp/arxiv/papers/1010/1010.1678.pdf

[Anonymous No.12108844]

>>12108345
thanks.

[Anonymous No.12108857]

>>12108824
I don't see anything about considering a particle in a box in it. The thing is that unlike the regular particle in a box, where the wave functions are sines, the Airy function doesn't have a constant distance between its zeroes, meaning that you need to take nasty linear combinations of Ai and Bi just to fix the boundary conditions. Still, the wave functions should be orthogonal. I'm wondering how much this fact helps in writing down an elegant solution.

[Anonymous No.12108864]

>>12108474
no, not all uncorrelated events are independent. the converse is true though

[Anonymous No.12108877]

>>12108691
I don't understand what you're asking. Is there any way to represent what? Airy functions?

[Anonymous No.12108898]

>>12108857
Oh, I see
For energies greater than c you should get sinosoidal solutions again, right?
Otherwise I have no idea

[Anonymous No.12108908]

>>12108877
>>12108898
Basically what I'm asking is if the orthogonal property of solutions of SL equations (of which Airy's equation is an example) can be used to find a solution that is not just approximate, but analytical. In order to satisfy the boundary conditions you need to fix zeroes at the ends, say at x = 0 and x = 1. But finding the exact linear combinations for this is difficult, because we don't know where the zeroes of the Airy function lie (analytically speaking, we can get numerical approximations though). I find it striking that such a seemingly irregular set of functions has the simple property of orthogonality, and it feels as if this can be used somehow to relate functions to each other, so we won't be doomed to solving everything numerically.

[Anonymous No.12108934]

>>12103457
I'm currently taking Fluids 2, looking for a youtube resource or solid univeristy lectures to watch

[Anonymous No.12108940]

>>12108908
yeah I think this is problematic just because of your "particle in a box" conditions. my best guess would be that for any energy less than C you'd only have a finite number of solutions until you get into the sinusoidal regime, so instead of needing to find an infinite spectra of airy functions you can just write out all the solutions by hand.
I don't know though because I'm also just physics and I've never had a two-sided box with a linear potential.

[Anonymous No.12108966]

>>12108940
The energy actually determines how much the Airy function is shifted, so you can get any zero of Ai(x) to lie at x = 0. I don't think you can do this analytically but it's still pretty basic. The real problem lies with fixing the boundary at x = 1, which requires a precise linear combination of Ai and Bi that is different for every eigenfunction, since the zeroes aren't periodically spaced (though they converge to a certain period).

Also I believe boundary conditions are necessary for SL problems. Oh well, thanks for looking into it for a moment.

[Anonymous No.12108977]

>>12108934
The ones you're paying for to attend.

[Anonymous No.12108983]

>>12108977
my professor is some fuck who has an accent thick as shit; if the lectures I paid for were good enough I wouldn't be here now would I?

[Anonymous No.12108990]

>>12106021
>>12106944
better suited for physics general if we still had one, the unfortunate part is that I can't just brush up on this subject and come back with an answer like I could for some analysis or PDE question.
If you showed some work and gave us some relevant equations in latex we would be more inclined to read up on your subject.

[Noko noko No.12109019]

Guys how do i solve 41 pls help, i get the values of 8 -36 and 27 for the quadratic equation, got something wrong on the way but can't figure it out

[Anonymous No.12109023]

>>12109019
>quadratic equation
>3 solutions
expand every term out and simplify until you have something ax^2+bx+c=0 and then solve the quadratic equation
you should only have 2 solutions

[Noko noko No.12109033]

>>12109023
I meant the values of a, b and c desu

[Anonymous No.12109040]

>>12109033
are you familiar with the quadratic formula? assuming you got a, b, and c correct:
[math]x= \frac{-b \pm \sqrt{b^2-4ac}}{2a}[/math]

however my guess is that you did some algebra steps along the way wrong because when I plug in your quadratic equation, I don't get the same solutions as when I plug in equation 41) to a solver.
I would start again

[Anonymous No.12109041]

>>12109033
You should have 8, -36 and 28.

[Anonymous No.12109074]

>>12109019
lmao

[Noko noko No.12109097]

>>12109040
Thanks a lot, i used the solver and realized where i was wrong

The solution is :

Let's solve your equation step-by-step.
(4x−6)2−(2x+1)(2x−1)=(2x−3)2
Step 1: Simplify both sides of the equation.
12x2−48x+37=4x2−12x+9
Step 2: Subtract 4x^2-12x+9 from both sides.
12x2−48x+37−(4x2−12x+9)=4x2−12x+9−(4x2−12x+9)
8x2−36x+28=0
Step 3: Factor left side of equation.
4(2x−7)(x−1)=0
Step 4: Set factors equal to 0.
2x−7=0 or x−1=0
x=
7
2
or x=1

The only part i didn't understand is (x−1) in part 3, where does it come from?

[Anonymous No.12109120]

>>12109097
do you know how to factor equations?
in step 2 I'd divide the last line by 4 to make things easier.
you have 2x^2-9x+7=0
then you factor this into (2x-7)(x-1)=0

[Anonymous No.12109169]

>>12108666
I don't know Satan, you tell me.

[Anonymous No.12109170]

Can someone help?
>>12108539

[Anonymous No.12109224]

Can anybody help me proceed with my Real Analysis homework? So far I have figured that I ought to take the contrapositive of the first problem, yielding
[math] \forall j \in J, \exists \alpha \in A(Y_\alpha \cap Z_j = \emptyset ) \Longrightarrow \exists \alpha \in A, \forall j \in J (Y_\alpha \cap Z_j ) = \emptyset[/math]

[Anonymous No.12109230]

>>12109170
there's no "reputable" online degree. your best bet is to just use the free online resources to get good at math and then prove your competency in other ways

[Anonymous No.12109309]

>>12109230
>there's no "reputable" online degree.
Explain Phoenix University, then.

[Anonymous No.12109312]

>>12109309
lol

[Anonymous No.12109320]

>>12109312
Not an argument.

[Anonymous No.12109331]

>>12109224
Have you tried taking X to be the set of all natural numbers?

[Anonymous No.12109335]

>molarity, molality, normality, formality
what were they thinking chemist bros?

[Anonymous No.12109336]

>>12109320
>listing the largest for-profit institution, known for shoddy accreditation and numerous lawsuits
>had to pay out millions of dollars of fines for false advertising
>the co-founder literally said it has "degenerated from a provider of working adult continuing education programs to a money making machine whose sole criterion for admission was eligibility for federally funded student loans"
you're right, it wasn't an argument. there doesn't need to be a valid argument against this """university"""

[Anonymous No.12109339]

what's the benefit of dividing things as intensive and extensive in thermo?
And why does In not considers substance in but Ex considers substance in not exterior?

[Anonymous No.12109341]

>>12109224
what is this math

[Anonymous No.12109349]

>>12109341
Real analysis, also set theory.

[Anonymous No.12109359]

can you get herpes from sharing an alcoholic drink

google says both yes and no.
And /med/ is no more

[Anonymous No.12109361]

>>12109341

[Anonymous No.12109385]

I've never jizzed in my undies while sleeping but few of my friends have due to sexy dreams, but I also unload every night before sleeping.
Is dream jizzing normal and is not doing it bad for health?

Also are there any chance of something going wrong if I keep masturbating nightly by humping my bed and jizzing in my shorts before falling asleep and keep wearing those same shorts for a month?

My penis head is also super dry and I don't experience precum majority of the times. I'm 32 btw if that's of any use.

[Anonymous No.12109393]

>>12109359
herpes is ridiculous, it sheds in skin and saliva and everything
might be a difference in viral load, idk. For medical stuff, use PubMed instead of jewgle

[Anonymous No.12109399]

>>12109385
https://en.wikipedia.org/wiki/Nocturnal_emission

[Anonymous No.12109422]

>>12109359
I have herpes, anon. The answer is 99.8% no. It requires skin to skin contact. That's why it's an STD.

[Anonymous No.12109448]

can someone explain universal properties to me like I'm retarded

[Anonymous No.12109458]

>>12108864
The question isn't whether uncorrelated implies independent in general, it's whether that's true in this specific case. Which it is. They're uncorrelated iff pq=1/3. And they're independent iff pq=1/3.

[Anonymous No.12109471]

>>12109335
most of this dates back to when alchemy was considered a legitimate science
wtf is formality though?

[Anonymous No.12109476]

>>12108666
just a guess, but wtf would the potential energy of an ideal gas be? temperature -> kinetic energy distribution

[Anonymous No.12109478]

>>12109471
Formality (F)
Formality of a solution may be defined as the number of gram formula masses of the ionic solute dissolved per litre of the solution. ... Commonly, the term formality is used to express the concentration of the ionic solids which do not exist as molecules but exist as network of ions.

[Anonymous No.12109641]

im the kinematics retard again, so turns out this prof really has it out for me, check my submission vs his solution
7 questions, 1 hour, including online submission, no time to check, yes i make mistakes.
but so does he, acceleration is not minimum at t=1/3 but rather at t=0 when accel is -1

the problem is find x position when accel 3t-1 is at its minimum x0 = 0

[Anonymous No.12109659]

>>12109641
Left is some of the worst handwriting I've seen.

[Anonymous No.12109676]

>>12109641
Did you get a grade yet?

[Anonymous No.12109679]

When people talk about quantum physics, what counts as an "observer" that makes the wavefunction collapse into a single event?
Let's take the cat box as an example-- is a camera an observer? A bacterium? The cat itself is also an observer? What do people mean that the cat may be alive and may be dead "until it is observed"?

[Anonymous No.12109684]

>>12109679
any measurement that interacts with the system
for example, a laser interrogating an atom is an "observer"

[Anonymous No.12109689]

>>12109679
>What do people mean that the cat may be alive and may be dead "until it is observed"?
That they read the wiki article and now think they're hot shit.
It was meant as a demonstration that the kopenhagen interpretation was nonsense

[Anonymous No.12109697]

>>12109684
What about two atoms colliding? Somebody taking a phone call 10 meters away sending EM through the experiment? This is a stupid questions thread right, does the "observer" or "measurement" have to involve some kind of intent?

[Anonymous No.12109702]

>>12109676
Zero / 10

[Anonymous No.12109703]

>>12109697
>does the "observer" or "measurement" have to involve some kind of intent
What do you mean by "intent"? Literally, interaction between electrons works here.

[Anonymous No.12109709]

>>12109697
no, there's nothing metaphysical about it
any observation can be boiled down to: "does what happened rely on knowing the quantum state of the system? if so, it was an observation"
if you have an atomic collision, the collision dynamics depend on the specific state of the atom. therefore, it's an observation of the state

[Anonymous No.12109711]

>>12109702
bullshit

[Anonymous No.12109722]

>>12109703
>>12109709
So do these "undisturbed" quantum states last for picoseconds at a time? EM radiation is a continuous wave, how do the quantum wavefunctions not collapse the very instant they form, if the smallest thing can qualify as an observation?

[Anonymous No.12109724]

>>12109711
I’m livid. He’s done this with all my submissions this semester

[Anonymous No.12109742]

>>12109724
I had a bitch ass teacher like that. He didn't like that I did my labs in blue text when I turned them in online, and he started deducting like 20% of my grade as a "penalty" for using blue text instead of highlighting.

[Anonymous No.12109745]

>>12109724
Did you politely ask for constructive feedback?
Or slashed his tires?
>>12109722
shut up and calculate

[Anonymous No.12109767]

>>12109724
Based prof.

[Anonymous No.12109775]

Boomer that has forgotten all the math he saw in high school here with a stupid question


I have 100 stuff that I have to distribute among a number of people.
The stuff is distributed not equally but according to a result they got.
The result is a number, people who got smaller numbers should get more than those with bigger numbers. everything should be proportional.

How do I do that

[Anonymous No.12109783]

>>12109775
be more specific and we can help, as of now there's no general method

[Anonymous No.12109794]

>>12109745
I’m gonna email him about this one, and about the first quiz. I emailed about my last post and he changed the grade, though not without a ticked response about how retarded it was to solve for time, and even if he changes them I’m still dropping in 2 months
But if he continues to do this I’m going to admin with muh evidunce. He complains in the announcements people don’t watch his YouTube videos from start to finish and I’m like the dude watching all his videos because I think he’s funny at 1.5x
What’s fucked up is I actually wanted to like this guy

[Anonymous No.12109799]

How can I solve for theta?

[Anonymous No.12109808]

>>12109799
Angle addition formula and maybe a combination with the other sin and another trig identity. If that doesn't work out, it's probably not analytically solvable. Can draw out your triangles to help but not convinced you'll get far

[Anonymous No.12109814]

Hello SQD. Was going to post this as a thread but glad to see theres a more appropriate place.

I'm analysing mouse brain sections for immunoreactive c-fos protein expression. I am currently trying to deal with some outliers.

My supervisor suggested i just delete the most extreme, but another lab member suggested i winsorize them.

My question is: When you winsorize a data point, shouldn't it be applied to all other variables to ensure you're not adding bias into the mix?

It doesn't seem right scientifically that i could just alter a data point and not do the same to other variables. Despite being ultra-conservative with p = 0.5 values and the like, the statisticians i'm learning off don't seem to have a problem blatantly changing an outlier

[Anonymous No.12109883]

>>12109799
you don't, what is the problem asking for specifically?

[Anonymous No.12109891]

>>12109883
It's the range for a projectile on a slope.
I want to find an equation for the an unknown angle of the projectile.

[Anonymous No.12109896]

>>12109891
you can't isolate theta in that equation

[Anonymous No.12109907]

>>12109896
actually this is a lie, but the expression is terrible and conditional on values of phi and also allows for multiple values of theta

[Anonymous No.12109950]

>>12109907
I don't think a single tenured faculty at my school could read through that without falling asleep.

[Anonymous No.12109960]

>>12109950
well it's showing six separate solutions. and for some reason it didn't simplify cos^2+sin^2=1 which I'm actually a bit confused about.
this is nothing though

[Anonymous No.12110000]

>>12109960
yeah, I just mean in general older professors get easily flustered with long computations. For ex I did some research with a professor who I also took calc 2 with years prior. He is a leading figure in mathematical physics but would get lost doing trig integrals in class for us lmao. I usually like these professors as they are big on elegant problems and solutions.

[Anonymous No.12110004]

>>12109907
What program/site is this?

[Anonymous No.12110009]

>>12110004
mathematica

[Anonymous No.12110459]

>>12103457
For an EE, specifically in systems and signals, what's best? A master's or a phd?

[Anonymous No.12110623]

>>12110459
What are your goals?

[Anonymous No.12110641]

uh is there another thread? why?

[Anonymous No.12110666]

>>12105980
Someone else already made the thread correctly. I don't have to be grateful for an inevitability, faggot.

[Anonymous No.12110669]

>>12110623
Honestly bro, to leave my shitty country.
On one part phd guarantees a salary whilst studying so that's a major bonus
On the other hand msc doesn't but it's shorter and I can ask for government aid or some shit to finance it.
It's immeasurably harder for me to find a good job in a foreign country than it is to find a position in gradschool and I also really wanna do gradschool and reasearch and shit.
Also want to be able to land a very comfy job after school

[Anonymous No.12111025]

Any math textbook that explains stuff more than just using symbols and saying stuff without saying words?

[Anonymous No.12111134]

How difficult would it be for a chemist to synthesise a substance they could quickly and realiably kill themselves with, like a potent poison or some kind of nerve agent?

[Anonymous No.12111326]

is there any way to faint naturally?
I once read about squatting+holding your breath and then jumping but i forget the specifics of such method

[Anonymous No.12111338]

>>12109775
Label the people 1, ..., n and let [math]R_i[/math] denote the result of person i.
I'll interpret
>people who got smaller numbers should get more than those with bigger numbers. everything should be proportional.
as follows: if [math]R_i = 2R_j[/math] (for example) then person j should get twice as much as person i,
that is: [math]I_j=2I_i[/math] where [math]I_i[/math] denote the amount to distribute to person i.
In general, the proportionality condition is [math]R_i/R_j = I_j/I_i[/math] which implies that
[eqn]R_iI_i = R_jI_j = \text{a constant } V[/eqn]
for every person, whose value can be calculated from [math]I_1 + \ldots + I_n = 100 = V/R_1 + \ldots + V/R_n[/math] to be
[eqn]V = \frac{100}{ \frac{1}{R_1} + \ldots + \frac{1}{R_n} }[/eqn]
and hence each person i will get the amount [math]I_i = V/R_i[/math].

[Anonymous No.12111546]

>>12105773
Okay.
By the by, the Latex guide has been revised.
https://imgur.com/a/9ecJ2zy

[Anonymous No.12111663]

>>12103457
How do I treat the rope in this beam problem?
Along side getting the reaction forces and moments in points I need to find out the weight of G neccessary to keep the thing horizontal

so do I treat it as a an angled force?
like for the x-direction

Fx=0 -> +
Fbx+Fg*cos45=0

[Anonymous No.12111671]

Why do we even need dx in [math]\int_a^b f(x) dx[/math]? I thnik it can be omitted and meaning of formula won't change

[Anonymous No.12111677]

>>12111663
yes

[Anonymous No.12111683]

>>12111677
ok thank you

[Anonymous No.12111695]

>>12111663
>so do I treat it as a an angled force?
Force by definition is a vector, so yes, you always have to consider its components.

[Anonymous No.12111697]

MATLAB or COMSOL?

[Anonymous No.12111699]

>>12110669
if it's india then gtfo of my board, pajeet.

[Anonymous No.12111702]

>>12111697
Comsol is pretty easy
Learning matlab is probably more useful as a whole

[Anonymous No.12111704]

>>12111699
stop using my numbers bitch

[Anonymous No.12111714]

>>12111671
fucking bump

[Anonymous No.12111715]

>>12111704
lmao why do internet pajeets always flail and puff their chests with national pride yet will do anything to leave for any remotely nice country to shit it up.

[Anonymous No.12111722]

>>12111671
it's just notation to specify what variable you are integrating with regards to.
[eqn] \int f(x,t) dx \neq \int f(x,t) dt [/eqn]

[Anonymous No.12111724]

>>12111699
>>12111715
Lmao not india

[Anonymous No.12111734]

>>12111697
MATLAB

[Anonymous No.12111742]

>>12111671
[math]f(x)\,dx[/math] is a standalone mathematical object, it's called a differential form. there's a theory of integration where forms are integrated instead of functions, it's useful. but before you learn about this, you can accept >>12111722 as the right answer

[Anonymous No.12111747]

>>12111722
I understand, but t is not always indicated, if it's then we can return dx (or dt), but it'd laconic to use short form [math]\int_a^b f(x) [/math] maybe....

[Anonymous No.12111768]

>>12111747
Then how would you know if [math]\int f(x) dx[/math] or [math]\int f(x) dy/math]?

The differential dx is there because integration is involves a sum over the values of f(x) and the change in a variable. If you remove the differential, then what you are saying is to sum all the values of f(x), but that's not what an integral is.

[Anonymous No.12111775]

>>12111768
>to sum all the values of f(x)
we keep b and a, so it's not a case.

[Anonymous No.12111786]

>>12111722
>it's just notation
No, it's not.

[Anonymous No.12111789]

>>12111775
a and b are just your bounds, that does not prevent the fact that it still means you are taking a limit over a sum of f(x) values. Also, if you have a multivariate function, how would you handle the integration constants (or rather, arbitrary functions) for indefinite integrals?

[Anonymous No.12111791]

Why is this true for a complex, normalizable [math]f(x,t)[/math]?
[math]\lim_{x\to\infty}x\left( f^*\frac{\partial f}{\partial x}-\frac{\partial f^*}{\partial x}f \right)=0[/math]
I understand that being normalizable implies [math]\lim_{x\to\infty}f=0[/math], and also [math]\lim_{x\to\infty}\frac{\partial f}{\partial x}=0[/math]. But then? There's also an x that goes to infinity, and infinity times zero is indeterminate

[Anonymous No.12111795]

Are there any practical applications of Lebesgue integration or is everything you'll encounter in the real world doable with Riemann integration?

[Anonymous No.12111806]

>>12111795
Neither physicists not engineers learn about lebesgue integration. That should tell you something.

As a rule of thumb any math beyond vector calculus might be interesting, but ultimately useless

[Anonymous No.12111809]

>>12111806
>Neither physicists not engineers learn about lebesgue integration
I did.
Only to calculate them through Riemann integration in the end.

[Anonymous No.12111811]

>>12111806
That's kind of what I figured, but I was just wondering since it seems to show up a lot in Fourier analysis which is a very applied field of math.

[Anonymous No.12111813]

>>12111806
I had it in a math for physicists class
Basically it was 'here it is, now you know it exists. Continue on as usual and if there's a problem contact your nearest mathematician'

[Anonymous No.12111815]

>>12111811
It does, but physicists usually handwave it away

[Anonymous No.12111819]

>>12111795
we know that stuff like differentation under the integral sign works only because of Lebesgue integration. so technically every time you do it you're actually using Lebesgue integral.

[Anonymous No.12111820]

>>12111811
My area is signal processing and I've never seen it used for anything other than masturbatory theoretic purposes

[Anonymous No.12111852]

>>12111811
the strength of Lebesgue integral is not that it can integrate more functions or that the computation is different/easier than Riemann integration (it's not). Lebesgue integral handles better the exchange of limit operations, stuff like differentation under the integral sign, "integral of sum is sum of integrals" etc, and for example in fourier analysis this is used all the fucking time. they just don't tell that to engineers because they don't need to know about it, but it doesn't mean it's useless. the results that they do know and use literally wouldn't be true without Lebesgue integration.

[Anonymous No.12111909]

If you multiply the same units do you multiply them too? [eqn]2min = (2min)(\frac{60s}{1{min}}) = 120s[/eqn] Then would following, rather absurd example be carried out in steps like this, or some others? [eqn]2min = (2min)(\frac{1min}{60s}) = \frac{{2min^2}}{60s} = \frac{(2min^2)}{1min} = 2min[/eqn] All I'm asking is if you treat units like variables or not?

[Anonymous No.12111926]

>>12111909
Basically yes

[Anonymous No.12111936]

>>12111909
Yes.

[Anonymous No.12111943]

>>12111926
>>12111936
Thanks

[Anonymous No.12112221]

https://math.stackexchange.com/questions/143222/what-does-dx-mean

is this guy mistaken with integral? Wouldn't it be

[math]\dfrac{uv^2}{2}[/math] and [math]\dfrac{vu^2}{2}[/math] ?

[Anonymous No.12112224]

>>12112221
Definite integral

[Anonymous No.12112239]

>>12112221
[math]\int _{0} ^{1} u v \ du = v \int _{0} ^{1} u \ du = v[\frac{u^2}{2}] _{0} ^{1} = v(\frac{1^2}{2} - \frac{0^2}{1}) = v(\frac{1}{2}) = \frac{v}{2}[/math]

Same thing for the other one.

[Anonymous No.12112346]

What's an example of a Cauchy sequence that isn't monotonic?

[Anonymous No.12112351]

>>12112346
1, 1/2, -1/2, 1/4, -1/4, ...

[Anonymous No.12112361]

>>12103457
Did I solve this statics problem correctly?
I had a beam and rope connected to another support

[Anonymous No.12112426]

>>12112351
Thank you.

[Anonymous No.12112433]

>>12111791
Explain context and notation, what is [math] f^* [/math]? Notation in Fourrier analysis and PDE varies widely.

[Anonymous No.12112449]

>>12112433
Sorry I should have said it, it's the complex conjugate of f. The context is quantum mechanics but I was too lazy to write out all the constants and stuff, f is the wave function

[Anonymous No.12112588]

>>12112449
If you find an answer please post it, I'm interested

[Anonymous No.12112789]

not a question but the notation used in probability is giving me fucking cancer
who in the fuck thought that you should represent a function using a capital letter, and its argument should be its lowercase equivalent

(or maybe it's the other way around??? I can't tell!!! the notation is fucking dumb as shit!)

[Anonymous No.12112800]

>>12112789
[math]P(X = x) = \int _{-\infty} ^{+\infty} f(x)dx = 1[/math]

[Anonymous No.12112961]

>>12112800
nope wtf man

[Anonymous No.12112981]

If I have some sequence [math]x_n[/math] and a convergent subsequence [math]x_{n=2k}[/math] is the limit of the subsequence always a cluster point of [math]x_n[/math]?

[Anonymous No.12113003]

>>12112981
yes

[Anonymous No.12113018]

How do I find the critical points with a denominator this messy? I looked at an solution online and they just completely skipped this step because they themselves didn't want to show the work either. The gist of what they did was that they looked a the numerator and just treated the denominator as if it was zero or something, I don't know....

[Anonymous No.12113026]

>>12113018
Denominator doesn't matter. If a/b = 0, then a = 0.

[Anonymous No.12113029]

>>12113018
Critical points are given when your derivatives are zero or are undefined. Your denominator does not affect f'=0 but it does affect f' = undefined.

[Anonymous No.12113036]

>>12113029
>>12113026
Holy fuck I completely forgot about this, this was taught back in Calculus 1 right? Thank you two so much!

[Anonymous No.12113070]

>>12113036
Cheers, lad.

[Anonymous No.12113181]

I feel like an idiot, but how come (b^3-a^3)/(b-a) is b^2+ab+a^2 and not b^2-ab+a^2
Isn't it step by step [math](b^3-a^3)/(b-a) = b^2+(-ab^2-a^3)/(b-a) = b^2 - ab +(a^2b-a^3)/(b-a) = b^2 - ab + a^2[/math]?

[Anonymous No.12113185]

>>12113181
Oh, I kept adding instead of subtracting

[Anonymous No.12113472]

Guys please help
I seem to be doing something wrong in this equation, but i don't know what it is

[Anonymous No.12113475]

>>12113472
You need more context.

[Anonymous No.12113480]

>>12113472
x=3-2y (top equation)
(3-2y)^2-4y^2=-3 (plug into 2nd equation)
9-12y=-3 (simplify exponents, the squared terms cancel)
y=1
plug into first equation
x+2=3
x=1

[Anomynous No.12113663]

While hooked up to an IV for water, is it possible for gastroenteritis to kill you from dehydration?

[Anonymous No.12113756]

>>12113480
Thanks a lot man, but how do i solve 51? I got stuck and i don't know why

[Anonymous No.12113797]

>>12113472
Lmao Solve using Newton rhapson

[Anonymous No.12113803]

I'm reading through "Physics from Symmetry" by Schwichtenberg, and I'm stuck on page 55. I'm fine deriving generators of SU(2) like [math]J_{3}[/math] and [math]J^{2}[/math], but then he writes that an abstract vector is used |b, m> and that [math]J_{3}|b, m> = m|b, m>[/math].

How in the ever loving fuck does that happen? What explicitly is |b, m>? I have never seen this notation in my life and he doesn't explain it at all. Literally out of the blue. It isn't a fucking column vector, because then [math]J_{3}[/math] doesn't hold for eigenvectors. If |b, m> is a 2 by 2 matrix that's fine, but then [math]J_{+}[/math] turns all 2 by 2 matrices to 0. I don't fucking understand what |b, m> is. Abstract vector my fucking ass. Can someone tell me what the fuck this thing is?

[Anonymous No.12113824]

>>12113803
Bro, the commands are \langle and \rangle.

[math]J_3|b,m \rangle = m |b,m \rangle[/math]

[Anonymous No.12113841]

>>12104022
Thanks bro. I ended up solving it a while ago but the troubleshooting i went through helped me understand organic chem that little bit more. Getting used to the naming and then being introduced to reactions is stressful esp when you have 3 other units to focus on.

[Anonymous No.12113854]

>>12113756
x+2y-2-xy=-6 (expand line 2)
x+2y-2-21=-6 (plug in line 1 to xy in line 2)
x=21/y (rewrite line 1)
21/y+2y-17=0 (plug in for x)
21+2y^2-17y=0 (multiply everything by y)
from here you can either factor or solve the quadratic equation for y
factored: (2y-3)(y-7)=0, gives you y=7 and y=3/2
plug these into xy=21 to get your two solutions for x (one solution for y=7, one solution for y=3/2)

[Anonymous No.12113870]

>>12113841
>esp when you have a normal workload to focus on
ngmi

[Anonymous No.12113871]

>>12113803
[math] |b,m \rangle [/math] represents something with total angular momentum b and angular momentum projection onto the "3" axis of m
so m can equal any of -b, -b+1, ... 0, ... b-1, b which for spin-1/2 systems is just -b or b

basically just an eigenvector of J3 with m as the eigenvalue, as well as an eigenvector of J^2 with eigenvalue b(b+1)
http://farside.ph.utexas.edu/teaching/qm/lectures/node38.html

[Anonymous No.12113893]

>>12113871
I guess that explains what b and m are which is helpful, but I still don't understand what the notation [math]|b, m\rangle[/math] is. If [eqn]J_{3} = \frac{1}{2}
\begin{pmatrix}
1 & 0 \\
0 & -1
\end{pmatrix}[/eqn]
then how do I write [math]v = |b, m\rangle[/math] so that [math]J_{3} v = \lambda v[/math]

In otherwords, how do I explicitly write [math]|b, m\rangle[/math]?

[Anonymous No.12113919]

>>12113870
Some people have to work and have hobbies faggit

[Anonymous No.12113923]

>>12113893
[math]|b,m\rangle[/math] is shorthand for [math]|b\rangle \otimes |m\rangle[/math] in seperable hilbertspaces, i.e. a matrix.

[Anonymous No.12113925]

>>12113893
I'm a bit rusty on representations, but see this: https://physics.stackexchange.com/questions/182506/correct-vector-space-of-eigenkets-of-angular-momentum

I think the punchline is that [math] |b,m \rangle [/math] is a convenient way of representing the J3 eigenstates that correspond to a specific J^2, since there are 2b+1 of them for each value of b.
you can write these [math] |b,m \rangle [/math] in terms of the spherical basis, see: https://quantummechanics.ucsd.edu/ph130a/130_notes/node210.html

[Anonymous No.12113939]

>>12113923
this is what I should've said
[math] J_3 |b,m \rangle = J_3 |b \rangle \otimes |m \rangle = \mathbb{I} |b \rangle \otimes J_3 |m \rangle [/math]

[Anonymous No.12113941]

>>12113939
put parentheses around the two kets in the middle term for added clarity, the things I realize too late

[Anonymous No.12113956]

>>12113854
Thank you thank you thank you!!
Anons like you are a blessing for humanity, this board is amazing

[Anonymous No.12113963]

>>12113923
It being a matrix makes sense. I guess then my question is, isn't [math]J_{+}v[/math] always 0? pic rel because i can't be arsed to latex matrices.
I must have made some kind of mistake, but I'm pretty sure doing [math]J_{+} = J_{1} + i J_{2}[/math] yields
[eqn] J_{+} =
\begin{pmatrix}
0 & 1 \\
0 & 0
\end{pmatrix}
[/eqn]

[Anonymous No.12113982]

>>12113963
Your v is an eigenfunction of J_3
So J_+ v = 0 because they don't commute
(that makes sense, right? I haven't done qm in forever)

[Anonymous No.12114006]

>>12113982
It doesn't make sense to me because then
[math]J_{3}J_{+}v = (m + 1)J_{+}v[/math] should just all equal 0 if [math]J_{+}v = 0[/math]
and if that's the case, what even is the point of a raising/ladder operator?

[Anonymous No.12114039]

Why are matrices so fucking gay with such retarded properties
god fuck
How do I get good at them? Any online lectures?

[Anonymous No.12114042]

>>12114039
>with such retarded properties
Such as?

[Anonymous No.12114067]

>>12113963
Why is c=d=0?

[Anonymous No.12114075]

>>12114067
Because [math]J_{3}v = mv[/math]. The v on the lefthand side has positive c and d, the v on the righthand side has negative c and d. Which numbers allow c = -c and d = -d?

[Anonymous No.12114092]

>>12114042
swapping sometimes turn them negative, sometime doesn't
what the fuck eigen values are even?
I don't even understand what's the point of them except solving linear equations?

[Anonymous No.12114096]

>>12114092
how much effort did you put into finding answers to your questions, anon?

[Anonymous No.12114099]

>>12114096
literally none
my head hurts and i want to kys myself

[Anonymous No.12114103]

>>12114099
>literally none
no shit

[Anonymous No.12114282]

>>12114092
Recall the basic picture that a matrix takes a vector and spits out another. An eigenvector of a matrix is a vector that doesn't change its direction after acting on it with M. It only rescales the vector. Every non-singular matrix has as many of these as the dimension of the matrix. The factor by which the eigenvector rescales is called the eigenvalue. Suppose you have a vector that you need to act upon with a matrix, then it's useful to write the vector as a linear combination of the matrix's eigenvectors, because they transform so easily.

[Anonymous No.12114411]

>>12114092
If a NxN matrix A has N distinct eigenvectors, it can be diagonalised: A=P.D.P^-1 where the columns of P are the eigenvectors and D is a diagonal matrix with the eigenvalues on the diagonal. Now consider A^k = (P.D.P^-1)^k = (P.D.P^-1)(P.D.P^-1)...(P.D.P^-1); the adjacent P^-1.P all cancel leaving you with P.D^k.P^-1. IOW, raising a matrix to an exponent simply raises the eigenvalues to that exponent, leaving the eigenvectors unchanged. Moreover, P.D1.P^-1+P.D2.P^-1 = P.(D1+D2).P^-1 and c(P.D.P^-1)=P.cD.P^-1. So any matrix polynomial applies the polynomial to the eigenvalues, leaving the eigenvectors unchanged. And this also applies to Taylor series, allowing you to efficiently evaluate analytic functions such as e^A for matrices; this commonly arises in the solution of systems of linear ODEs: dx/dt=Ax => x=Ce^(At) where x is a vector and A,C are matrices.

Also, because multiplication of diagonal matrices is commutative, multiplication of two matrices with the same set of eigenvectors is commutative: (P.D1.P^-1)(P.D2.P^-1) = P.D1.D2.P^-1 = P.D2.D1.P^-1 = (P.D2.P^-1)(P.D1.P^-1).

A NxN matrix which doesn't have N *distinct* eigenvectors can't be diagonalised; such matrices are termed "defective". A defective matrix always has repeated eigenvalues (repeated roots of the characteristic polynomial), but not all matrices with repeated eigenvalues are defective.

[Anonymous No.12114415]

>>12114411
great answer, I'm sure the anon now gets it

[Anonymous No.12114419]

>>12114415
shut the fuck up faggot

[Anonymous No.12114426]

>>12114419
>autistic screeching intensifies

[Anonymous No.12115118]

>>12114411
Based.

[Anonymous No.12115843]

Will I be able to get a good grade in a Linear Algebra exam (retake) I have in 3 weeks?

For reference, studying computer science 2nd semester uni is TUM.

[Anonymous No.12115894]

>>12115843
Are you going to try?

[Anonymous No.12115939]

>>12115894
I am, but I have a lot of lectures to watch, which I'm afraid will be very time consuming. I've watched like 4 and I have 20 more.

[Anonymous No.12116252]

G-guys how do i solve this equation? If i isolate x in the bottom equation i get x=3+y and then if i put it in the top equation i get that x equals - 1, when the right answer is 1
Where did i go wrong?

[Anonymous No.12116301]

>>12116252
I don't know how you are solving it, by doing those same steps I get a quadratic equation for y, and one of the answers does require y=1 (not x=1). Check your calculations because the method should be correct. If you wanna know where exactly you went wrong then post your progress too
And there's also a second answer, but I don't know that's the one you are looking for and in fact none of the answers imply x=-1

[Anonymous No.12116383]

>>12116252
FWIW, the solutions are x=-3,y=-6 and x=4,y=1.

Solve one of the equations for one of the variables, and substitute that into the other equation to get a quadratic. E.g. solving the second for x:
x-y=3 => x=y+3
Re-arrange the first:
4/x-2/y=-1
=> 4y-2x=-xy (multiply by xy)
=> 4y-2x+xy=0
Substitute x=y+3:
4y-2(y+3)+(y+3)y=0
=> 4y-2y-6+y^2+3y=0
=> y^2+5y-6=0
=> (y+6)(y-1)=0
=> y=1 or y=-6
y=1 => x=4
y=-6 => x=-3