/sci/ - Science & Math

I'm trying to programmatically draw a circle (A) with an ellipse on top (B) to make it look 3D.
I know the coordinates and radius of A, the radius of B, the angle between A and B, and a ratio on a Z axis.
I need to find the distance between them / the coordinates of B.
The best way I can think of doing this is finding dx and dy and subtracting those from A's coordinates. The problem is I have some examples of what B's coordinates should be and I'm missing a multiplier to get the final coordinates.

For example:
> A coordinates: 239.01, 503.28
> Radius of A: 40
> Angle: -0.15666801971794328
> Radius of B: 6.868199456661592
> Z axis ratio: 0.8890140261948463
> What B's coordinates should be: 233.87,535.84

Is there any formula to do this?

I don't have any uni course until September but I have access to the registration of the lectures of the past years. I'm thinking of watching just one of them (I'm going to have 3 courses on September), and then in September I'll rewatch the whole course but in real life (but the lectures will be basically the same) and then take the exam in January. Everyone I talk to tells me this is a retarded idea, is it?

>>15548345
You don't have enough information to calculate d, at least not with what you have written. Also wtf is a z-axis ration? The eccentricity?

>>15548418
Good to know. What information would I need to calculate it, if possible?

> Also wtf is a z-axis ration? The eccentricity
Yeah, sorry about that. I'm pretty bad at explaining things and pretty shit at math.
The z-axis ratio thing is essentially the ratio in 2D and 3D lengths between an object in front of the A and A itself. Like drawing a cylinder out from B. Sorry again for the shit explanation.

>>15548250
is the equation for hydrostatic pressure enough to figure how much pressure the titan submersible was experience or are there other parameters i should consider?

if the universe is so big, then why won't it fight me?

>>15548691
one could argue that just by living you are working hard to fight the universe. Universe is always trying to kill you.

Is there any website that can give you unlimited math / equation questions to puzzle out? It would help balance out memorizing various formulae. I tried using chatgpt but math isn't its strong point.

I get why {q_i,p_j}=δ_ij
But in some exercise my professor used that {r_i,p_j}=δ_ij
How is position the same as the generalized coordinate? I mean, as far as I know the ith component of the position vector doesn't have to be the same as the ith generalized coordinate.

If a component of the angular momentum is constant, wouldn't it imply that all components of the angular momentum are zero?
Let's say Lx=0, then since {f,c}=0:
{Lx,Ly}=0=Lz
{Lz,Lx}=0=Ly
{Ly,Lz}=0=Lx
Does it make sense?

>>15549249
No. You need to look again at the definition of Poisson brackets, it uses the derivatives of the variables and not the actual components. Saying L_x = 0 just means the object is rotating about the x-axis, L_y and L_z do not have to be zero. Stating {L_y, L_z} = L_x = 0 means angular momentum is conserved in the y-z plane.

>>15549300
What do you mean? The definition of a poisson bracket is
[math]\{f, g\} = \frac{\partial f}{\partial q^i} \frac{\partial g}{\partial p_i} - \frac{\partial f}{\partial p_i} \frac{\partial g}{\partial q^i}[/math]
So, if Lx is constantly 0
[math]\{Lx, Ly\} = \frac{\partial Lx}{\partial q^i} \frac{\partial Ly}{\partial p_i} - \frac{\partial Lx}{\partial p_i} \frac{\partial Ly}{\partial q^i}= 0 \frac{\partial g}{\partial p_i} -0 \frac{\partial g}{\partial q^i}=0[/math]
And since [math]\{Lx, Ly\}=Lz[/math], then Lz=0.

>>15548250
>tfw i love math so much but dont have the brain power to go deeper

i am cursed with dumbassary

>>15549310
You seem to be overlooking the fact that notation implies a sum. Just because [math]\frac{\partial L_x}{\partial x} = 0[/math] does not mean the other terms for y and z are.

>>15549489
If Lx is constantly 0, then over any partial derivative it will be 0 bro...
{f,c}=0 is a well known result, look for it in Landau page 135.

Please help with my measure theoretic probability theory project. I'm trying to maximize the probability that I find love within my lifetime. Any suggestions?

>>15549249
Your calculation looks good to me but can't you just argue that angular momentum zeroes at the origin, hence if it's constant it's zero everywhere?

>>15549819
Something I'm not getting is that imagine a spinning wheel. The angular momentum perpendicular to the direction of rotation is zero but clearly the total angular momentum is not.

am i retarded or do most proofs require you to already have seen how to prove them to be able to prove them?

>>15550159
Yeah, I think I just remembered the issue.
If you're taking Poisson brackets you're working over phase space, by definition, so your "constant angular momentum" needs to be independent of not only space, but also momentum.

>>15550376
For anything non-trivial, regurgitating a known proof is much simpler than devising a proof from scratch. This is essentially the P vs NP issue. Simpler proofs often follow from the definition of whatever you're trying to prove.

If a real number [math]a[/math] satisfies [math]0 \leq a < \frac1q[/math] for any [math]q \in \mathbb N[/math], then that means [math]a = 0[/math] right? I'm trying to prove this by contradiction, but I'm getting stuck trying to show there's a smaller reciprocal between 0 and a. Any hints?

Hello right now I'm taking Calculus III for the first time. Is there a good intuitive way to think about moments, as they pertain to mass, torque, center of mass, intertia, radii of intertia, etc.? I get what's going on with mass and, to a lesser extent, torque/center of mass, but I'm lost when it comes to what the second moment means mathematically and why it's used for intertia. I've never taken a physics class before so these physics concepts are kind of bewildering.

>>15550775
whoops I meant radii of gyration, not radii of intertia.

How do i prove this?

a and b are integers. if a divides b and b divides a, then a = b or a = -b.

>>15550879
depending upon precisely how you have defined "divides", this would suggest that [math]|a|\geq|b|\geq|a|[/math]

>>15550913
thank you anon, does this work for: [math]\exists z \in Z, b = za [/math] for a divides b?

Is it weird I can solve equations in the abstract, but find it harder to solve them when applied to practical problems?

>>15550946
It should, but it'd need a couple of more steps.
let a=zb and b=na
then a=z(na)=(zn)a, so zn divides 1
since z,n are integers, it follows that either z=n=1 or z=n=-1

Any good book for electrodynamics which teaches all the pre requisite calculus required and how it's applied in most problems ?(mostly integrals)

>>15551137
kek good one

study calc 3 an some diff eq then find any old electrodynamics book

Can someone please help me with this exercise?
Let P=b*T^4 and E=3*b*V*T^4, with b a positive constant. Find F(T,V) and S(T,V).
Since I need S to calculate F, I decided to go for S first. But when I do the integral I got some constants that depend on T and V. My result was: S = 8bT^3*V + C_1(T) + C_2(V). What can I do to get rid of those constants?

>>15551117
ty anon. how can i show [math]5^{n+1} \geq 2^{n+1} + 3^{n+1} [/math] if i know [math] 5^n \geq 2^n + 3^n [/math] ?

i was trying [math]5(5^n) \geq 5(2^n + 3^n) [/math] but i cant manage to get the RHS to match

>>15551435
Don't use five on the right side, use (2+3).
Distribute properly and drop the two middle terms
to conclude the right hand side.

>>15551448
ty anon, i think that's where i got stuck, i end up with [math]2^{n+1} + 3^{n+1} + 2(3^n) + 3(2^n) [/math] but i couldn't figure out how to get rid of the extra terms

>>15551463
>>15551448
Just drop the extra terms. In terms of the inequality,
a sum with four terms is always greater than a
sum with two terms.

>>15551474
ah that makes sense, thank you very much anon

>>15550702
The rational numbers are dense in the real numbers so you can find a rational number [math]\frac{p}{q}[/math] in the open ball [math] ]0,a[[/math]. Then it's easy to see that
[eqn] 0 < \frac{1}{|q|} < a[/eqn]

Or you could just use the Archimedean property of the real numbers.

This might sound very retarded, but I'm genuinely curios and worried. Is it dangerous to bath/shower during thunderstorms? Could lightning travel through water pipes and potential kill you?

>>15551861
If lightning somehow strikes the water pipes it's already grounded. It is going nowhere after that.

Can somebody explain how do we get the concept of observable universe?
How is that galaxies are travelling apart from each other at a speed more than that of light?
And what prevents the light from them to not reach us? A star's light travels at every direction, so wherever those galaxies are travelling apart from us, some of their lights would still go into our direction anyway.

>>15551874
Because the 'effective' velocity of a galaxy moving away from us is their relative velocity + the rate of expansion of the universe. This speed can be more than the speed of light. It's like a car driving along a road between two cities but the road keeps getting longer so the car will never reach its destination.

>>15551883
Not fully understand your analogy, but that would only sound true if the rate of expansion outspeed the speed of light. And to my knowledge, light always travels at c from any perspective.

>>15551889
It is the space between objects that is expanding. Nothing is travelling faster than the speed of light.

Also note that the more distance between two points the faster the expansion will happen. So as space expands the rate of expansion increases, so there will come a point where the two points are no longer causally linked - even at light speed they can no longer 'see' each other. That is the edge of the observable universe.

Why is every job boring and brain dead? I got a PhD in math 9 years ago and in the best case scenario I get hired because employers telling clients I have a PhD in math is some shinty impressive credential but I’ve never needed to do anything that took me more than a week to learn at most. I’m so bored and disappointed with how boring work is bros. I even became a “professor” at a “professional studies” school recently and even here it’s boring af.

>>15551941
> Why is every job boring and brain dead?
They aren't. You have just done a shit job at finding something you enjoy doing.

Is using vectors and matrices the only way, or most efficient way, to solve triple integrals? If so, why? Does this mean that single and double integrals can also be solved with vectors and matrices, or is it just triple? I "passed" a Calc 3 class, solved the problems the way I was instructed, but I simply do not understand the connection between vectors, matrices, and calculus. Enlighten me. I've never taken a linear algebra class nor studied it in any significant capacity yet, so my limited understanding of vectors and matrices came from precalc.

>>15552020
There is no single method to solve integrals. All mathematicians have is a set of tools they can try and use to solve specific ones. The methods you were taught worked because the questions were chosen so that they would.

In Atoms and Molecules, Weissbluth brings up that it is useful to write the density matrix in terms of the spin matrices (and thus the pauli matrices), why is it so?

>>15548250
I'm trying to obtain pic related without having to use stirling gamma aproximation or gauss multiplication theorem and take the particular case, but this is behaving like a bitch, not like the Legendre's duplication formula which is nice and tame.
Any suggestion/hint for this?

>>15552066
You didn’t answer any of my questions.

>>15552295
The most efficient way to solve an integral depends on the specific integral. There is no best or only way to solve a double or triple integrals, it is conditional on the question asked. As for "solved with vectors and matrices" you need to give context since we don't know what you are talking about, that can cover a multitude of methods.

>>15551947
Tell me an interesting job

>>15552433
That's a question only you can answer.

I just learned that my grandmother was a technical assistant in math to a Dr working on materials engineering problems with the equivalent of a 2 year degree. She also used Fortran and ALGOL in the 60s without formal education.
How smart would someone have to be to do this, as a woman, in the 60s?
Thanks.

>>15551941
>I even became a “professor” at a “professional studies” school recently and even here it’s boring af
Of course it's unsatisfying: you're teaching some meme subject you know no one cares about

>>15552464
You mean she was a code monkey? You don't have to be particularly smart to be one of those.

>>15552524
What's a "code monkey"?

>>15552559
> A computer programmer who is not involved in any aspect of conceptual or design work, but simply writes code to specifications given
What is a "search engine".

>>15552566
You're obviously really smart. A lot smarter than me. Good for you.

>>15552464
Fortran and ALGOL aren't hard programming languages.
Honestly the only "hard" programming languages are C++ and Rust. Everything else is pretty simple.

>>15552582
Thanks. I always thought she was really smart. Is the math related to materials science hard? She said she was doing what I think translates to differential equations, tensor(?) calculus, and math related to chemistry and atoms.

>>15552595
Sounds like she was using numerical methods to solve such equations. There is now entire field related to that topic since it affects every area of modern science. It's amusing she was using FORTAN since despite it being archaic it is still widely used to this day, there is a *ton* of legacy code out there that is core to many areas of science. A good example is CERN which has been using FORTAN for over 50 years. Some of the underlying physics libraries their software uses is still written in FORTAN 77 - if it ain't broke, don't fix it.

thoughts on this guy?

https://en.m.wikipedia.org/wiki/Grigori_Perelman

tl;dr: He declined the millennium prize problem and fields medal because he believed that the global math community degraded into a fame-hungry group of mathematicians instead of solving problems for the better of the community.

if there are any grad students in this thread, is this true?

newb to maths

am I right in thinking that the distributive law works for addition/subtraction/multiplication but not for for division? e.g. you can do what's in the brackets first and then multiply or multiply the values

3 x (8+2)
3 x (8-2)
3 x (8x2)

all of the above can be done either with brackets first then multiplication or multiplication or each value in the brackets (distribution) and then the operation.

but

3 x (8/2)

would give a different result if done brackets first or distribution first.

so is it right to say that distribution works for everything except division?

>>15552685
always do brackets first then distribute

>>15552696
that doesn't answer my question

>>15552685
>3 x (8x2)
distribution only applies with different operators. multiplication with multiplication like this is just basic associativity, which also applies to division.
unless you want to suggest that 3x(8x2)=3x16=48 is equal to (3x8)x(3x2)=24x6=144

>>15552706
okay that's association
but can you answer my question about it not applying to division?

>which also applies to division
i dont get what you mean by this

>>15552708
division is just a specific type of multiplication; anything you can write as division can be easily rewritten in strictly multiplicative terms
3x(8/2) is equivalent to 3x(8x0.5)

>>15552712
but unless rewritten and left as a division operation then distribution won't work right?

>>15552716
distribution doesn't work in this context anyway; see the multiplication example
in a more general context where distribution does work, since division is just a subset of multiplication, it necessarily obeys all of the same laws that multiplication does, although they might need to be rewritten slightly to account for things. if multiplication is distributive in a given situation, division is also necessarily distributive. if multiplication is not, division cannot be, either

>>15552721
thanks for not answering my question

>>15552723
it is wrong to say that distribution works for everything except division

>>15552725
i'm talking about a simple example where you have one value outside of brackets and two values inside brackets being divided

>>15552685
In terms of the order of operations, distribution
works fine for adding and subtracting because
they're lower in order. Multiplication and division
doesn't have this property and could at best have
associativity since (x) and (/) are in the same level.

>>15552757
how would division have associativity? can you explain with an example

>>15552773
3x(8/2)=3x4=12
(3x8)/2=24/2=12

>>15552787
that's changing the values though
i mean division isn't distributive when in brackets

>>15552757
>>15552773
Okay, take the one you had, 3 x (8/2), and
compare with (3 x 8) / 2 . Parentheses (or brackets)
are top of the order and whatever's inside are
done first. Both give the same result, 12.

I meant to say that division does not have
true associativity [compare (12/4)/2 vs. 12/(4/2)].
But, when you're using (x) and (/) you can group
them differently with parentheses and it's fine.
And, of course, multiplication has true associativity.

>>15552818
yeah but my point is that

number x (number/number)

doesn't give distribution. right?

>>15552818
>>15552827
No, it does not. That's reserved for the lower order
operations (+) and (-)

>>15552830
does it matter how many low order values there are in brackets. for example can you do

number x (number - number - number - number)

or must the brackets only have two values for distribution to work?

>>15552663
That's really cool anon. Thank you for the insights! I'm not sure if she was using the IBMs for numerical methods to solve the equations but she definitely used them to interface with some sort of graphing computer or module or something. She said she was really excited to be able to work with those things. I love my grandma so much bros.
>FORTRAN 77
>77
That's a lot of versions lol.

>>15552830
>>15552835
Yes n x (n-n-n-n) is fine since you can distribute
to all four terms inside the parentheses.

>>15552846
Nah, it just means 1977 when it was first proposed
to replace FORTRAN [19] 66.

Maple have the year attached on their software,
for example.

>>15552864
Well, this is clearly not my home board :)
I don't even work in STEM. Thanks again and have a good day.

>>15552857
and you can do the parenteses first obviously?
so the number of values doesn't change anything?

What's a language like C or C++ but with first-class arrays, but still pointers and explicit dynamic (heap) memory?

>>15552873
>>15552857
Correct.

>>15552878
thanks

>>15552202
bump

>>15552478
Yep. I failed to get a math postdoc a long time ago and now I am doomed to roam the earth teaching the kids of Chinese communist party members some bullshit buzzwords to put on their resume so they can enter buzzword field of the day.

>>15552877
Rust?

I'm trying to culture some mushrooms in agar because I'm a degenerate but also curious. I have access to them but really want to do it myself. I have read loads of guides on shroomery and followed what seemed to be best practices, building a still air box, reading about sterile procedures, agar formulations, etc.

I bought two spore swabs and tried to inoculate three plates. I saw minuscule growth on the plates after about two weeks but let it go because sometimes it takes that long, I read. Today I inoculated four plates using the other swab and I want some second opinions about what could be wrong if these plates don't take. The main thing I did differently was to swab more aggressively, turning the swab continuously and sort of scrubbing the swab onto the agar surface, making sure to transfer whatever was on there.

I think there's a few things that could be the problem if these don't take: 1. The swabs were dead when I bought them, 2. The agar formulation I used (potato-dextrose-agar) is not suitable as I have made it, 3. My sterile procedure's bad and the spores were outcompeted. I don't think this one's the case because after nearly 6 weeks at room temperature my plates have basically no growth on them.

Thoughts?

IQ TEST QUESTION:
I came across a picture with no context on another board. I got two solutions but I am not sure which one is the correct answer.

option 3 could be right if we match the patterns row-wise and rotate every picture with 2 dots in it by 90 degrees to the right and just add the one in the middle column "on top of the one in the left column" (I think it's the AND operator). my issue with this solution is the fact that there is a conditional in this solution(if there are two dots, rotate) and the condition isn't met in the second row, which would provide feedback whether the observed pattern in the first row is correct.

the other possible solution for me is option 2. I group the patterns by the top right to bottom left diagonals and apply XOR operator to the one in the first and second rows, and then apply XOR operator to the result and the one in the third row. the two diagonals each give the same result (dot in the right, bottom and left). if I try to apply these operators to the "3rd" diagonal, I the last element should be option 2 to get the same result.
with this method, my issue is that it could be "overcomplicated" and I'm "using" a 4th image (the result) as well in every diagonal, instead of only using 3. however, this method is less ambiguous to me due to the fact that I apply the exact same operators to the corresponding elements in the same order

what would the correct answer be? is it possible that there are multiple choices that are correct?
on what basis should I decide which one to choose? should meta data such as the supposed difficulty of the question influence my choice?

>>15553957
> I came across a picture with no context on another board.
It's almost certainly a shitpost. These kind of pictures are more often than not fake, or a misprint, and are made to make people argue since you can apply various logical arguments and get different valid answers. For example you could just as easily say the number of dots per row or column must be 4 or 5, so the answer is option 6.

Consider the vector space of functions defined on the interval [0, 1], that have a non-zero value on at x = 0.5. So this is a vector space of non-continuous functions with a "point" somewhere on x = 0.5. The Riemann-integral is a linear functional of its dual vector space (all of these functions are Riemann-integrable with value 0).

My question is: Is the Riemann-integral equivalent to the zero of the dual space? Or is the Riemann-integral actually a distinct non-zero linear functional that happens to map all elements on zero?

>>15553957
These tests are designed in such a way that even smart children could solve them in a minute or two. I don't know the answer (or if there even is one) but it's certainly not as convoluted as your proposed solutions.

>>15554012
I don't usually do iq tests, what part of my solution was convoluted?
in my opinion the XOR operator isn't necessarily harder than the AND operator.
with the first method there is even a condition, which makes it "harder" in my opinion
is the diagonal step what makes it more convoluted?
>>15554000
ok, thanks
the conclusion is that there should only be one answer, instead of multiple correct ones

I have a follow up questions though, the solution that gives 3 as the right answer is ambiguous to me (the fact that in first row you have to use the condition unlike in the second row).
is it possible to encounter such questions in a proper test? would it be a valid train of thought to assume that it's not the right answer given the circumstances?

>>15554045
In a real IQ test you would get a long list of these type of questions to answer in some short period, like 15 or 30 minutes. It is not only about being right, it is about be fast too. So if someone posts a question like this that takes more than a minute to reach a logical singular answer there is clearly a problem.

>>15554045
In a (good/decent) real test you won't encounter
>multiple possible answers
>conditionals or patterns that don't manifest everywhere
>weird expected grouping/ordering (though some tests could be designed differently for cultures that are used to reading right to left, for example)
>expected knowledge that a 7 year old wouldn't have (though something like XOR isn't totally unreasonable)
>a very long thinking time (even 5 minutes per question is considered way too much)

>>15554057
>>15554064
thanks a lot, it all makes sense now

Where do I find online math courses, especially on more advanced topics that are harder to find? I'm specifically looking for courses from places like coursera. Anyone know where I can find a download link of Coursera's Complex Analysis course?

>>15552877
C++ has std::array tho.
>>15554002
>this is a vector space
It's not, it doesn't have a zero.

>>15554121
zero would just be the zero-function. Yeah I made a mistake by saying they're all discontinuous, obviously the 0 polynomial is

>>15554121
std:: classes aren't "first-class" since they essentially libraries and not native data types.

i'm a computer scientist currently working in IT, and i don't feel particularly close to my colleagues. a lot of them didn't go to college and don't understand anything about maths, computer science, algorithmic thinking, or logic.
i honestly feel closer to someone who studied mathematics than i do to someone who works as a system administrator or network engineer in IT

>>15554170
>>>/soc/

>>15554182
i'm not looking for friends, i didn't ask a question either, it was just a disjointed comment i guess

Any anons here who have access to the Nature journal who can upload a PDF of this?

"Income and inequality in the Aztec Empire on the eve of the Spanish conquest"

It's not on scihub or libgen

https://libgen.is/

can you trust this address or will I get a virus from downloading anything from there? What is the "official" libgen web address?

I need the following proposition in my proof: The restriction of an inner product (bilinear, symmetrical, nondegenerate) is a bilinear form.

Would you say this is trivially true. Or do I have to write a separate lemma for this?

>>15554421
restriction on a subvectorspace of course

>>15554417
I've never had issues downloading anything from libgen, at any address

>>15554138
std are first-class since they're part of the spec.
If you're going to argue std isn't first class then C doesn't have first-class heap manipulation, since you need to import the stdlib to call malloc, but C++ does, since you can use new.

>>15551154
Calc 1, 2 3 have different definitions world wide. Some people do calc 1 in school itself and some till calc 3 in freshman itself. By calc 3 you mean curl divergence ? Analysis or surface volume integrals ?

One more thing, I think it's a little tough to connect the dots with physics based problems

>>15549249
Poisson brackets (or commutators in QM) between angular momentum components and some other physical quantity F tells you how F behaves under spatial rotation. So the mutual Poisson brackets of the angular momentum components are just telling you that (Lx, Ly, Lz) rotates as a vector. If you are setting one component to zero over all phase space then naturally the other components must be zero everywhere too by rotational invariance. This just means your system is completely invariant under spatial rotation, there is effectively no physics in the angular directions

>>15548399
Retarded in that you'll be missing out on summer as an opportunity to do something you want to do
Not retarded in that learning twice is always better than once
Retarded in that the course is designed to be doable in the common way by most people on the course
Overall, depends how retarded you are and if you're willing to potentially waste life opportunity

>>15552706
>unless you want to suggest that 3x(8x2)=3x16=48 is equal to (3x8)x(3x2)=24x6=144
sorry to return to this but yeah why doesn't the distributive property work for multiplication of values in parentheses but only addition/subtractoin? e.g. why doesn't:

3 (2 x 4)

this is gives two different answers if you do the parentheses first and then the outside multiplication or if you multiply the values in the parentheses by the outside value then multiply them together.

Why doesn't the distributive property work for multiplication?

>>15554489
>calc 3 you mean curl divergence ? Analysis or surface volume integrals ?

yeah this stuff plus some vector field stuff from diff eq

>One more thing, I think it's a little tough to connect the dots with physics based problems

i dont disagree but physics became much easier once my math background became much more solidified. so it shouldnt be that much of leap to apply those concepts you learned

>>15554889
Distributivity, in a general sense, is essentially "spreading" one operation out among another. You can't distribute an operation among itself.
Plus, if it worked that way, it would flagrantly violate associativity.

>>15554960
can you give a simpler answer? i'm a retard

>>15554971
might be easier to explain why that would be problematic with an actual example.
if multiplication was allowed to distribute across itself, we would be able to do the following
(a*b)*(a*c)=a*(b*c) (distributivity?)
=(a*b)*c (associativity)
=c*(a*b) (commutativity)
=(c*a)*(c*b) (distributivity?)
=(a*c)*(b*c) (commutativity)

that leaves us at (a*b)*(a*c)=(a*c)*(b*c)
then if we divide both sides by (a*c) we find that (a*b)=(b*c), for any values of a,b,c, with the sole caveat that a*c cannot equal 0 (else we would be dividing by 0 in the final step). which would kind of render the operation completely useless

>>15554991
you lost me
nevermind

>>15554994
in short: we can't define it to distribute across itself because it would make very big contradictions

>>15554971
> it just works
the rules are defined as they because that makes them consistent.

>>15554971
If multiplication is distributive then it should apply to all numbers
Suppose a(bc)=ab + ac
Then ab+ac=a(b+c), so
a(bc)=a(b+c)
Dividing both sides of the equation by a gives us
bc=b+c, which clearly is not true for all numbers

This is called a proof by absurdity

Question for you: when does
bc=b+c?

Anyone know what is up with phys.org? It's not loading this evening.

>>15554078
self boomp

what dilutes radiation?

>>15555077
space

Why cant i do

[math]\forall x \exists y ( x > y) \\ \exists y(x > y) \ UInst \\ (x > b) \ EInst \\ \forall x(x > b) \ UGen \\ \exists y \forall x (x>y) \ EGen [/math]

I know I can't, but which rule specifically am i breaking?

>>15554889
By algebraic structure, terms are held between
(+) and (-), like 3x + 4y - 6z...these are three terms.

The product is what makes terms while addition
and subtraction separates terms. As such, you
can distribute between two or more terms but
you can only multiply to make terms bigger.
Associativity can work in each term, but is not
guaranteed across different terms.

>>15555082
>which rule specifically am i breaking?
Generalization.

>>15553957
maybe it is a very high IQ test (160-190+). these types of tests give you essentially unlimited time to solve, eg one question can take days.

>>15554138
If it's part of the spec it's part of the language, regardless of a) whether it's in the std namespace or the root namespace and b) whether or not you need to include a header to get a declaration.

If you want to make a language/library distinction, the closest thing that C++ has is the distinction between freestanding and hosted implementations. std::array isn't required for freestanding implementations, although this is up for discussion for C++23. Heap-based containers will probably never be required for freestanding implementations, even though "new" itself is.

>>15555223
how would you know? you have never taken such a test.

trips and i commit suicide

>>15553957
you're gonna hate this princess

>>15555082
you can't replace the order of the existential qualifier. when you remove "b". you need to go back (wrong generalization there).

the last line shows the Universe is bound below. your sequence is
true for {-1, 0, 1, ...}
not true for R

the first line shows the universe has at least 2 elements
true for {1, 2}
not true for {1} (not because of the quantifiers, but because 1>1 never holds)

stop sperging
on the first line ∃!y in place of ∃y would make them equivalent i'm 95% sure

What great wisdom did >>15555555 bestow upon us?

In order to show that a mapping is a sesquilinearform it's sufficient to prove that is first Hermetian and second linear in the second argument, right?

I'm a web and app designer and I wanted to create a functional and pretty interface for a periodic table of elements, as an exercise.

What do you use when you need to check the periodic table? A poster, a book, a web page, a mobile app? What do you think is most important about it? Is there a functionality you miss?

Best I got was this one, but I still think the interface is clumsy: https://pubchem.ncbi.nlm.nih.gov/periodic-table/

so the reason the sky is blue is due to scattering.
And the bright spot in the center of our sky is the non scattered cone of light coming from the sun.

what would 12'noon look like if we took away the cone of light from the sun but left the blue scattering? how bright would it be and is there more visible light than just blue there?

>>15555746
> so the reason the sky is blue is due to scattering.
A common misconception, that is only part of the real reason. Shorter wavelengths are scattered more than longer ones, so purple is scattered even more than blue. However due to the nature of the human eye we are more sensitive to blue than purple light which is why we see a blue sky rather than a purple one.

>>15555746
> what would 12'noon look like if we took away the cone of light from the sun?
huh? if you took away the sun there would be no light at all.

>>15555792
>huh? if you took away the sun there would be no light at all
I did not explain it well.
I’m wondering what it would look like if the main bright spot in the sky was gone, but all the light that would be scattered by the atmosphere is still there. It’s not a real situation, because to block that spot would mean to block the sun, and then no light would be scattered.
Maybe see what I mean? Would everything be purple blueish, if so how bright?

>>15555849
It would look a darker blue since all the unscattered white light would have been removed.

If I restrict a scalar product on a vectorspace V onto a subvectorspace U, will it be a scalar product on U?

>>15555849
It is a real and common situation. Direct sunlight may be hid by clouds. Nothing amazing happens.

>>15555932
That is because you still have all the indirect sunlight.

Can someone explain why area is measued with square units? Why not any other shape? I don't get why it's squares?

>>15556090
Ask yourself what is the simplest 2 dimensional shape that tiles seamlessly.

>>15548250
I am looking for functions that fulfill the following criteria:
not differentiable at x=0
|f(x)|≤x2
functions I have found thus far
>pic rel

>>15556155
I meant
>|f(x)|≤x^2

>>15556090
It makes the formula for the area of a rectangle nice and simple. You could use another shape, it's just mean adding a constant factor.

>>15556111
I don't know what you mean by tiles seamlessly.
>>15556157
>adding a constant factor.
What?

>>15556203
>I don't know what you mean by tiles seamlessly.
you can cover a plane with it without leaving any gaps and without any overlaps.
Technically the actual simplest would be an equilateral triangle, but a square is more intuitive given that its sides are strictly orthogonal

>>15556207
Does the square unit even have to be the same? Can't it be like inches on one side and centimeters on the other side.

>>15556210
I suppose, in theory, you could do inch-centimetres if you really wanted to.
But that would make you a bad person. With no friends. Because everyone would despise you for being such a bad person.

>>15556215
so same units used because they are the simplest way to measure units and squares are used because they are the simplest shape?

>>15556222
More-or-less, yes.
Same reasons apply to cubic units in three dimensions

>>15556225
it's weird because you don't even have to have something be added up to a square unit for it to be measured in square units.
for isntance you could have a rectange which is 1/2/ cm on one side and 2cm on the other side and the area would be 1 square cm even though there isn't even a square cm.
can you explain that?

>>15556236
split the rectangle in half the long way
you get two 0.5x1cm rectangles side-by-side
relocate one to be on top of the other and fuse them back together
and there's your 1x1cm square

>>15556240
Yeah I see what you're saying that you can alter the shape but I'm having tough time understanding why it's even called a square unit at this point

>>15556246
the short of it is that a plane is two-dimensional, so you, obviously, need two dimensions to measure it along
so we want to divide the plane up as simply as possible into sets of parallel lines (our x- and y-coordinates). if we measure with a parallelogram of some sort, we find that we only need two of these sets, because each of the parallel sides conveniently fall into the same set as each other.
if we tried with a triangle (the simplest shape), or anything more complex than a parallelogram, we find that we need to introduce more of these sets of lines to divide the plane. so we pick the easy option and just go with a parallelogram.
next, we would like these lines to be evenly-spaced so two points separated by the same number of lines are always the same distance apart, for ease of measurement. that narrows down our options for measurement to some sort of rhombus.
lastly, we pick the square in particular just because its axes are at right angles to each other and it would look a bit dumb otherwise.

I realise this explanation might be a bit hard to understand, so picrel is a shitty diagram intending to demonstrate each of the addressed alternatives, with a triangular measurement scheme in the top-left, a rectangular one in the top-right, a rhomboidal one in the bottom-left, and the square in the bottom-right. The colours are intended to represent our different axes of measurement (our parallel sets of lines). Apologies if it's still a bit unclear; it's never really a question I've thought to address, nor have I ever seen anyone else take it on

>>15556297
Though I should also note that there's nothing actually wrong with the rhombus one besides it looking stupid. In fact, it'd measure exactly like the square one does, since a rhombus and a square of the same side length have the same area.
We just like it better when our dimensions are perpendicular to each other

>>15556297
>>15556303
thanks and really appreciate the effort
basically area is 2 dimensional so you need units that are also two dimensional and squares are the easiest unit to use because all sides are the same size?

>>15556331
That's pretty much the gist of it, yeah.

>>15556334
thanks man

>Assume you have a bilinear map between two real-valued vectorspaces. Is the extension of this mapping to a sesquilinear map on the complexification of that vectorspace unique?
Chatgpt says 'yes'. Can someone confirm that this is correct? Seems logical, but I want to be sure before I go about proving it.

>>15555019
They're back online but no news posted today. Can anyone with a twitter account check to see if they posted anything? (I don't have an account)

>>15556240
By the way can I ask if this can be done with any shape? Is it possible to rearrange any shape into square units through splitting and relocating?

>>15556452
You could in theory, although a much easier procedure in general than figuring out how to make everything fit together is to simply split the shape into a bunch of squares, measure those individually, and sum up their areas.
To return to your rectangle example, we could split the 0.5x2 rectangle into four 0.5x0.5 squares, each of which would have an area of 0.25 cm^2. Since there are four of them, that'd total an area of 1 cm^2

>>15556472
when are square units not usually used? i'm new to maths so what's the newb answers for square units and area

>>15556482
or is it the case that area is only calculated when the figure has only two sides? so anything beyond two sides is not possible?

>>15548250
I has had a curious and butiful image in my mind for a while, I will start with sharing it to entise ouy to math for me:
>clear borosilicate tube
>vacuumed to low pressure with a hint of cold blue argon under enough excitation
>also present is a dye with Am-95, sputtering it's ionizing alpha beads in a plume
Now, if the ionizing effect of helium cores isn't by themselves enough to excite the argon >Ionization energies for argon:
> 1st: 1520.6 kJ/mol
> 2nd: 2665.8 kJ/mol
> 3rd: 3931 kJ/mol
How small amout of external electrical field would it take to just get the tracks of the alpha particles to light up?

I image it locking like a cloud chamber with blue streaks of light instead of condensed alcohol tracks. And it would glow for ever and ever.
If radon builds up it would even get a never before seen purple tint.
(◕‿◕) (ʘ‿ʘ)

>>15556203
Like you could use circular feet instead of square feet, and you'd get x circular feet = pi*x square feet. And then the formula for the area of a rectangle with sides x and y would be x*y/pi.

>>15556532
>cold blue argon
>a never before seen purple tint
Ionized argon IS violet, you tard dumbass!
Only with added mercury it gets the cold blue color, stupid!

>>15556602
so when newbs learn about the difference between perimeter and area is that basically in the context of squares/rectangles then?

>>15556617
(,◕ ◕,) (ʘ︿ʘ)

>>15556621
He's right. The Townsend discharge would cause the whole tube to glow, not just the streaks after the alphas as happens in air saturated with alcohol.
>At low voltages, the only current is that due to the generation of charge carriers in the gas by cosmic rays or other sources of ionizing radiation. As the applied voltage is increased, the free electrons carrying the current gain enough energy to cause further ionization, causing an electron avalanche. In this regime, the current increases from femtoamperes to microamperes, i.e. by nine orders of magnitude, for very little further increase in voltage. The voltage-current characteristics begins tapering off near the breakdown voltage and the glow becomes visible.
picrel by Dougsim - xer own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=22286660

>>15548250
Is it possible to charge an object to the point it tears it's self apart through electric repulsion? Is there a scenario that could enable this? Why or why not?

>>15556620
Not really? The area of a circle with radius one foot is 1 circular foot or pi square feet, the perimeter is pi feet. The perimeter and area have different units, and they only come out to the same number if you use square feet.

>>15556664
>the current increases from femtoamperes to microamperes, i.e. by nine orders of magnitude, for very little further increase in voltage
So if tap this we literally have free energy?????
Looks like the fieldkeepers have dona a big messy up in here! \Ö/

>>15555223
the issue isn't that you can't find patterns in it
the issue is the fact that there are multiple possible answers

>>15556679
Hm. Yes... Yes, it does.

>>15553957
It's 2. Simply, there are three 1 horizontal line dots, three 1 horizontal 1 vertical line dots, yet only two 2 horizontal line dots. One of these things is not like the other. The options available also help sus out the relevant pattern.

>>15556709
I feel I did a poor job explaining. Vertical and horizontal are incorrect terms to describe the pattern. Dot orientation is a better term.

>>15556713
Me again, You can think of the circiles in the following ways:
0 degrees dot group
90 degrees dot group
180 degrees dot group

Each of these have three circles, where one of the three circles is rotated 90 degrees (the odd man out).

Number two is the answer because it fulfills this pattern by being the odd man out of the 180 degree group.

I hope this helps :)

>>15556722
You haven't read the thread have you. The question is bullshit.

>>15556006
The indirect sunlight is the scattered light you are talking about.

>>15556737
I don't understand. It clearly has an answer, and the answer is 2. The poster of the question was not using pattern recognition and instead leveraging his academic knowledge. From what I understand, IQ test questions are supposed to be universal.

>>15556757
Such questions are meant to have a single answer. There are three valid ones in this thread already.

>>15556759
Any of the 3 dot options would be major outliers. That narrows it down to option 2 and 6. From there I believe it is obvious. I think with this question the pool of answers is not a bystander, but a tool used to solve the problem. I respectfully disagree with you sir.

>>15556770
And I say your answer it too complex and a case of over-fitting the given data. But you do you.

>>15556757
at the highest IQs though there is no clear line between academic knowledge and intuitive knowledge

someone with an extremely high IQ may be able to intuit many advanced concepts and ideas that most people require a formal education to understand, especially in areas of math and logic.

>>15556850
I agree, and I will add that setting expectations are important for any test, especially with something as potentially subjective as pattern recognition.

A superconducting electromagnet holds its "magnetization" forever, right? So in order to shut off a superconducting electromagnet, it takes energy, correct?
Would it be correct to assume that conservation of energy requires that it takes more energy to shut off a superconducting electromagnet when it's stuck to a massive neodymium magnet than when it's not holding anything at all?

Best book for self studying physics ?
Resnick halliday Krane, Serway jett, Roger and youngman ?
Also pls give few tips on how to self study from these books as this is my first time taking a calculus based physics course

>>15556931
> A superconducting electromagnet holds its "magnetization" forever, right?
Only in 'persistent mode' - you put a current into the superconductor and them form a closed loop - and then only in an idealized magnet. In reality the magnetic field would very slowly decay due to something called flux motion resistance. That can still take months.

> So in order to shut off a superconducting electromagnet, it takes energy, correct?
Depends on what you mean. You could remove the current (take energy out) or raise the temperature abuse the critical value (put energy in).

> Would it be correct to assume that conservation of energy requires that it takes more energy to shut off a superconducting electromagnet when it's stuck to a massive neodymium magnet than when it's not holding anything at all?
I can't see how, if anything it would take less since energy is extracted from the magnetic fields when two magnets stick together (it is doing work). You put that energy back when you pull them apart (which is where energy conservation comes in)

I made a thread, but probably should have put the post here..
>Decide to re-read Physics for Scientists & Engineers 4e - by D. Giancoli
>See picrel on page 16
>Green arrow pointing in the wrong direct??
>Am I retarded or is this an error

>>15557314
In your own words, you're retarded. The charge will attempt to equalize between the two rods. So positive charge will flow from the rod with the excess charge - but that means in actuality electrons are moving in the other direction.

>>15556757
what academic knowledge was used in the original solution?

How do I do this?

Can you give me an example for a positive definite sesquilinearform that is not Hermitian?

>>15557496
Calculate the double integral.

I'm a /tv/ fag and I don't know shit about math. So bear with me please. Include the steps if you provide a solution.
If a+b=12 and ab=32, what is the value of (a+2b)2 - 5b2?

>>15557376
>>15557314
To elaborate, positive charge does not actually flow, only negative charge does

>>15557855
[math]a,b[/math] are clearly the solutions of the equation
[eqn]0 = (x-a)(x-b) = x^2 - (a+b) x + ab = x^2 - 12 x + 32[/eqn]
You can solve it with the quadratic formula.
[eqn]x_{1,2} = 6 \pm \sqrt{6^2 - 32} = 6 \pm 2[/eqn]
which means either [math](a,b) = (8,4)[/math] or [math](a,b) = (4,8)[/math]. In both cases you can just plug those values into the other expression.

I've been working through Spivak and I'm getting filtered hard by some of the proofs. I get the general idea behind induction, by cases, contradiction, etc, but I can't figure out how to get from point A to point B. Anybody had a similar problem? How can I build my mathematical intuition? Should I just keep trying to grind away at Spivak until it clicks?

Today I met an electrical engineer that is retarded. It was like finding out santa claus isn't real. I always thought engineers are smart. I want my innocence back.

>>15557929
Less caffeine, more sleep, eating right, 10-30 min of elevated heart rate a day (cardio), and most importantly of all DON'T PANIC. If you are backed into a corner and freaking out about how to catch up, you have already lost. Imagine some one in a marathon trying to catch up in the last hour. You need to be calmly learning this stuff and putting in the time early and consistently. This way leads to less stress and less hair loss. I speak from experience.

>>15558154
The jobs they are given turn them retarded. It's like the people in the movie "Walle". You don't use it, you lose it.

Hey /sqt/ /qtddtot/, I'm having difficulty finding a high resolution star chart for northern and southern hemispheres. Everything I find is low res or a garbage interactive sky map. Anyone have any files or leads?

>>15558482
Nvm, found this for my purposes which is good enough.

>>15557125
Bump, best beginner calculus physics book ?

How can we calculate maximum postion of a particle if the problems are given in the form of xyz coordinates ?

Like velocity = xi+yj
Acceleration= gi+hj...find magnitude and position ?


How to tackle through these type of problems ?

>>15558709
Any pre 2015

at high enough pressure wouldnt liquids be condensed into becoming solids?

does the bottom of our oceans not reach that threshold for water?

at a given orbital height, to burn in the opposite direction of the orbit to make the object fall into the thing it orbits, i guess it would take more thrust/energy for something of higher mass. but if theres no air or anything in space to oppose it, i have a hard time intuitively understanding why the same amount of thrust or force wouldnt move an object of any mass the same amount

You guys I'm a total idiot and can't into this beginners science class I'm taking as a non-science major. Could any of you help me out with this homework problem? I'd be grateful.

A 0.6kg squirrel hops off a tree branch and falls towards the ground. At a height of 3 meters, the squirrel possesses a speed of 7.67 m/s. How tall was the tree branch?

Using the formula for kinetic energy and potential energy (0.5*mv^2 and mgh) I found that KE = 17.65 and PE = 17.64 at 3 meters. I just don't know how to find out how tall the tree branch is.

>>15558882
hint: total energy is conserved in such situations
hint 2: the squirrel had no kinetic energy when it was on top of the branch.

>>15558871
Yes, they would. The pressure at the deepest ocean reaches around 500 atmospheres, but to solidify water would require over 10000 atmospheres.

>>15558880
Newton's Second Law: F = ma, so a = F/m

The thrust you generate (F) gives less acceleration to more massive objects.

>>15558882
Another hint: is the squirrel did not "leap" it fell off the branch. "Leap" can confuse things.

>>15558894
>>15558920
I appreciate the hints but they're not working

>>15558952
Sum up the kinetic and potential energy of the squirrel to find the total energy of the system. (It's more complicated in reality, but in a class like this this is intended.)
This total energy is constant for the squirrel.
When the squirrel has no kinetic energy, its potential energy is ____, implying that its height is ____.

Wait a sec, if I have its kinetic energy, which is 17.65J, isn't this its maximum kinetic energy? Meaning the same thing as its total energy? If TE = KE + PE, and its KE can only be a max of 17.65J, then that would mean that at that point in time, its PE would = 0. Is this correct?

>>15559006
Meant for >>15558964

>>15559006
> isn't this its maximum kinetic energy
no, it is still 3m above the ground. the squirrel has some more distance to fall before going splat.

>>15556422
Two days now and still no new articles :(

>>15559025
So if I simply add up its KE and PE at 3m, I'd get 35.29J. This is its total energy?

>>15559037
Correct.

>>15559040
And now that I have its total energy I can rearrange the PE formula to find height, which gives me 6 meters! Ahhh thank you for the helpful advice! I'm wasn't adding up the two numbers initially because I thought that the KE I had was its maximum energy possible, not what it had at 3 meters. I didn't put together the fact that the formula for KE accounts for velocity at the given moment so it got me all confused. Much appreciated!

Please: >>71578002

>>15559104
whooops >>>/fit/71578002

>>15548250
I have to animate an eyeball rotating in 2D like in picrel. I have the radius of the iris, but don't know how to get the distance from the center of the eye. Is there a formula to do that?

What's the standard to plot a function [math]f: \mathbb{C}^2 \to \mathbb{C}[/math] ?

>>15559924
or at least a function [math]f: \mathbb{C}^2 \to \mathbb{R}[/math]

I have an electromagnetic-thermal-statistical question:
Why does EM radiation come off an object at all, instead of just being canceled out?
For a simple example, black body radiation.
The way I understand heat energy is the kinetic motion of particles in an object moving around randomly.
The way I understand EM radiation is a wave of force polarized in the direction a charged particle gets accelerated.
And black body radiation being a result of heat in an object with charged particles.
But if a given particle in an object at a given moment in time gets jerked to the right, and emits EM radiation polarized to the right, wouldn't it be likely that at the same moment, somewhere close by, there is a particle with an opposite charged also being jerked to the right, or a same charged particle jerked to the left that would cancel or almost cancel out the EM force?
Even with 3 degrees of motion and continuous time, wouldn't an object of several trillion trillion charged particles emit a net zero EM force at a certain distance?

>>15559981
It is nothing more than the vibrational energy of the body being converted into EM radiation (low energy photons). The lattice vibrates in all directions so the radiation is emitted omnidirectionally. The EM field generated by those vibrations is too small to affect neighbouring atoms so you can think of them being isolated.

>>15559981
I think you are misunderstanding EM waves. They aren't the same thing as the instantaneous Coulomb force. They are physical and carry energy, momentum, and angular momentum. Even if all the multipole moments of a set of charges vanish on average, so there is no average force far away, there will still be radiation emitted.

>>15554406
>>15554406
>>15554406
bumping

would this be cost-prohibitive or what's the catch? are there chemical processes that are feasible to do in a home lab for profit? meth is a popular meme but how about things that aren't necessarily illegal or dangerous

When does the current of a lightning strike actually flow? I'm trying to reason about it in my head. The lightning bolt traveling from the cloud to the ground (or vice-versa) doesn't actually represent a current flow; strictly speaking it's not really moving, rather it's a stationary-but-growing plasma channel. Once the plasma channel and the other surface (assume cloud to ground, so the ground) unite, that's when there's actually a conductive path for the current to flow.

Is that about right?
I'm wondering about this because I'm trying to reason about the strength of the inducted magnetic field from a lightning strike, which given the average strike is 30000 amps over the course of ~50 microseconds (hence the above question), I want to know why lightning strikes don't cause magnetic objects to jump a foot off the ground

>>15560972
> The lightning bolt traveling from the cloud to the ground (or vice-versa) doesn't actually represent a current flow
What the fuck are you talking about? Yes it does. You literally contradict yourself by later talking about 30000 amps.

> I want to know why lightning strikes don't cause magnetic objects to jump a foot off the ground
Lightning strikes cause EM pulses detectable hundreds of kilometers away, they can also magnetize nearby materials such as rock and metal.

>>15561016
>What the fuck are you talking about? Yes it does. You literally contradict yourself by later talking about 30000 amps.
t. failed a critical reading comprehension check

As I understand it, the propagation of the plasma wave is just the continuous ionization of a ribbon of air. It's not instantaneous (read: doesn't immediately contact the ground), and as the plasma is a fantastic conductor, it must necessarily be at more or less the same voltage as the region of cloud-charge the lightning started from. There is no large net current flow in the lightning as it propagates downwards, before it has contacted the ground.

However, once it DOES contact the ground which IS at a different voltage potential, the charge is free to flow resulting in that 30,000 amp current

>>15561047
There is a displacement electric field between cloud and ground due to free charges, typically in the clouds, but positive lightning is also a thing (ground to cloud).

>>15560747
its exceptionally hard. there's a reason medical cocaine is extracted and not synthesized.

Quantum tunneling is inversely proportional to the size of the potential energy barrier, so does that mean that superinsulators, having infinite electrical resistivity, prevent quantum tunneling altogether?

>>15560972
>>15561047

I think you are confusing two different phenomena. Arcing and sparking.
Arcing happens when a voltage difference through an insulator becomes so great that atoms and molecules get broken down creating a conductive ribbon, like you said.
Sparking happens when a mass of charge gets to the point where the pressure and other factors spontaneously causes a column of charged matter to get rocketed off the surface of the mass. The long thin shape of the column allows other columns to get rocketed of the ends. This repeated process creates a web of charged matter in the air. When one if the tendrils of this web contacts a conductor, that's when the main discharge happens.
Lighting is based of sparking, not arcing. If you watch those slow motion videos of lightning strikes, you can actually see the charged web being built up and glowing before the actual strike.

I'm not sure why you don't think lightning doesn't cause magnetic fields. People have long reported things like iron cutlery being thrown around and magnetized when their house gets struck by lightning.

>>15561233
I see now, that definitely clears things up. It's not that I don't think lightning causes magnetic fields, I was actually thinking the opposite, that it should cause magnetic fields and magnetic effects but I haven't ever heard of it happening. Evidently I'm just under-researched and under-informed, I never knew about the cutlery. That's interesting.

>>15561246
Part of it is that the duration of the strike is so short that the magnetic field generated by the time-varying current is short -lived. Plus, the inverse square law dictates the mangetic field strength, so it falls off quickly with separation.

>>15561233
>>15561246
>>15561253
Hold on real quick. I agree that there's a different mode of electrical phenomena that I wasn't aware of (ejection of charged material), but I'm not sure if "sparking" is right. Wikipedia gives this as a definition:
"An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an ionized, electrically conductive channel through a normally-insulating medium, often air or other gases or gas mixtures."
this is pretty much what I described, so what is the term for the other discharge phenomenon?

>>15561266

Okay, seems like I have made a mistake. Both sparks and arcs involve electric breakdown at some point. Now if I am going by my old assumption, arcing happens spontaneously with an extremely high voltage field between two charges. While sparking can happens at lower voltages and is kicked off by the introduction of charged matter in the field.
But I could be wrong, because now I am seeing that some people describe sparks and arcs as the same thing, and that arcs are just sustained sparks.
Going back to the lightning example, it now makes sense that there is a breakdown. I assumed that either positively or negatively charged matter can happily travel along without affecting the neutral air much. But there would have to be a violent breakdown of the air for the charged web to glow like that in those slow mo videos.
Seems to me that when charged matter gets ejected off a long thin object, it does induce breakdown of the air to get those effects you see, like sparking, or corona discharge or St Elmo's fire

>>15561104
That's not how superinsulators work. Electric charges are confined into charge neutral excitations much like quarks are confined into hadrons. You seem to have in mind that there is in infinite potential barrier or something

I have been trying since really long, but still not able to understand concept integration in electrostatics and most of the integration based questions in electrodynamics ?

>How to take element in integration ?
>Flux ????
Am I getting filtered here ? Pls help

>>15561468
Are you getting filtered? Yes, but you're in good company. It's the subject that filters the most undergrads by a large margin. It is the first time many encounter such concepts and that level of advanced mathematics.

How do you define components in a vector space, if you have an uncountable basis? In this case, you can't order the basis, so you have a problem. How do you deal with it?

Homework wants me to "compare" the Chebyshev norm to the Euklidean norm. Okay, but do they want me to actually do here? Just writing out what the differences between the definitions is? It can't be that easy, right?

>>15561932
Why can't it be that easy?

>>15562024
The prof is an asshole that tries to fuck students over with trick questions.

>>15562031
The only trick possible there is arguing over the meaning of 'compare'.

>>15562034
Question is only one point, anyways. I guess I'll go with that. Thanks

>>15561916
>so you have a problem
No u. They don't need to be ordered, they only need to be indexed.

>>15562323
How do you index a set that has no bijection to N? Do you assign real numbers randomly (presuming there's no ordering relation on this vector space)? Can you give me example of such an indexing scheme?

[eqn]\langle U^\perp \rangle = U^\perp = \langle U \rangle^\perp[/eqn]Is it true? The brackets denote the linear span.

>>15562333
The set of indices could be any set you want. You can think of this indexation as a function [math]f:\mathcal{I} \rightarrow X[/math] whose domain is the set of indices, and for every [math]i \in \mathcal{I}[/math] we denote [math]x_i = f(i)[/math].

Nice digits, by the way.

Any rigiours algebra book that covers high school algebra (quadratic equations, progression series, stats geometry and trigonometry) ? For self study ? Other than art of problem solving

Something like spivak of algebra ?

I have to show this equality [eqn](U^{\perp})^{\perp \perp} = (U^{\perp \perp})^{\perp}.[/eqn]But isn't this identity trivial, since [math]U^{\perp \perp}[/math] is just a notational shorthand for [math](U^\perp)^\perp[/math]?

>>15562389
Thanks for clarifying

I'm trying to build a cumulative distribution function on some data I have. The x-axis of course will be the ordered data points. Do these, or should these, be unique? In other words, if there are duplicate data points in my dataset, should I exclude those from the cdf?

pic related, this dataframe has 13 rows, whereas the original dataset has 15 rows. The duplicates are condensed, and so the cdf plot will have no vertical lines.

>>15562548
>proportion adds to greater than 1
Fixed that mistake. Here's the plot of that cdf

I know what a set is and what a tuple is
but is there a name for an unordered collection that allows duplicates

>>15562868
Multiset

>>15561468
look into line integrals, surface integrals and volume integrals.

If you havent seen this kind of math then it will be hard for you. Unfortunately physics education will not change because it is run by people who huff farts and got into their positions through networking. Not because they care about teaching

(i wish to be proven wrong though)

Is there any android app where I can get daily updates on the latest scientific papers in a certain field? I tried the arxiv one, it kinda sucks and all others require registration.

>>15563509
you're wrong. the explanation much simpler. they got their jobs because they are good at physics, not because they are good teachers. they are two very different skillsets.

>>15563843
fair point. but networking means the relied on politicking into a position of perceived prestige/power

How does statistics work with data that naturally wraps around itself. :Like say I want to see if there is a relation between what time of the year someone is born in and how tall they will be. Someone on the 365th day of the year is very similar to someone born on the 1st day of the year, but all the normal tests and measurements would be under the assumption that they're the furthest apart

How exactly does one go about conducting research? I have 0 idea about these things, but I wanna do research in college. I wanna know how the process goes from start to finish.

Why do 90% of people fail the Wason 4 card test?

>>15548345
Why do you need Z if its 2D?

>>15563956
The 7 card only, or?

>>15564002
Oh I'm a retard and forgot A was a vowel. That one as well.
>>15563956
To answer your question, most people are retards, as I have immanently shown.

>>15564007
According to the usual statistical breakdown you must be a very very special brand of retard, almost everyone lists the A but few list the 7.

>>15551889
Each local region is expanding under the light limit, but the distance is so vast that after a particular distance the cumulative expansion of all inner regions is greater than the speed of light.
That distance defines the observable universe as light beyond that distance will be stretched out to zero before it can reach us.

>>15552955
In no expert but perhaps try your setup using a generic easy to find fungi.
>something from a supermarket so you can check if the correct thing is growing.
training wheels...
How are your light levels?

>>15562486
bump

>>15563956
If you want to know if the rule is true for every card you need to turn over every card.

>>15563956
it's basically 4 tasks all at once which is annoying to keep track off with 100% accuracy in your working memory, you're normally supposed to write each step down instead of doing them all in your head

[eqn]\left(U^{\perp} + W^{\perp}\right)^{\perp \perp} = \left(U \cap W\right)^{\perp}[/eqn]I want to show this equality for infinite-dimensional vectorspaces. Would you say I need functional analysis for this? (Or is it easier if you apply it.)

Why doesn't MIT release their 6.013 and 6.014 (Electromagnetic waves related) courses?

Any other good resource to learn EM waves and transmission lines? I'm looking to go into RF IC design further.

Am I stupid? How do I make it?
I've taken this test every couple months in the past 3 years and consistently got 135. I was doing it to see if it was consistent and also to see how bad my brain damage affected my intelligence.
I got brain damage a few years ago and now my short term memory is diminished and multitasking is really hard
I've felt pretty stupid my whole life, everyone says Im good at math, and honestly I'm not really good at anything else and the apartment my family lives in is too small to expand into this also.
How do I make it?
I've turned into a social retard since my brain damage

>>15564307
Thinking IQ matters does indeed show you have brain damage.

>>15564317
I don't think it's the sole factor, but probably does indicate my ability to solve shape puzzles which might correlate with other ability.
Read my post, I explain more of my problems.
I don't think I'm some genius guy, I feel pretty stupid a lot, I'm just looking for a way to be successful in spite of my problems.

>>15564329
Your questions are better suited for /adv/ than here.

>>15564347
>JUST DROP 120K IN COLLEGE BRO
>JUST DO TRADES BRO
yeah no... I need smart people to help me

>>15559936
Usually you use colours. Like red is high blue is low.
>>15561932
I'd state the definitions, then I'd differentiate their respective unit circles, and finally I'd bring up that that the Euclidean norm comes from an inner product and hence respects the parallelogram law.
>>15562339
Yes.
>>15562486
Looks good to me.
>>15564166
Can't see why you would.
>>15564307
>multitasking is really hard
I'm almost convinced being awful at multitasking is actually a good thing. It prevents you from becoming a complete ADHD zoomer.

>>15564353
>>15559936
>Usually you use colours. Like red is high blue is low.
Nvm I read [math]\mathbb{C} \to \mathbb{R}[/math]. I dunno how you'd go about graphing a function on 4-dimensional space.

>>15564353
>being awful at multitasking is actually a good thing
yeah but it makes it really hard for me to do multiple classes at once

>>15564375
I'm sorry, when I read that you were bad at multitasking I interpreted it as being bad at doing multiple things at the same time, not doing multiple things in general.

>>15564379
I guess I mean i'm REALLLLLY bad at it
I've done some community college but I really don't think I'll make it through real school.

>>15563940
Depending on the field that you're getting into this
list might differ but it's essentially like this:
>have an idea (crucial starting point)
>write a hypothesis or thesis statement
>forget what you seen/heard (prevents bias)
>gather materials (books, tools, etc)
>comb through your materials and note them
>many questions? seek answers!
>is your statement okay? if not, fix it, you know more now
>develop methods/experiment or practice your knowledge
>did the experiment or practice worked out? if not, fix it
>gather data and draw conclusions from test or practice
>does it confirm or deny your hypo./ thesis statement?
>yes? present results; no? present results, save info
>save info and practice for further research, read list again

>>15564353
If andonly if the underlying Euklidean or Unitarian vector space is one-dimensional, the Chebyshev norm comes from a skalar produkt, too. Because then, the parallelogram law is fulfilled. Doesn't contradict with you post, but it's an interesting trivia, I think.

>Can't see why you would.
My problem is this inclusion [eqn](U^\perp + W^\perp)^{\perp \perp} \supseteq (U \cap W)^\perp[/eqn]I was able to solve it for finitely-dimensional U and W using the orthonormal basis of the vector space V. In the case of infinitely-dimensional U and W, you can't use this argument, of course, because orthonormal bases don't necessarily exist.
I think the problem might be of whether of not an infinite-dimensional U and W is complete; in that sense that all Cauchy-sequences converge. This would then require functional analysis.
U and W are subvector spaces, I forgot to mention this in my original post.
Do you know if an argument for this inclusion exists that only utilizes methods from linear algebra?

>>15564413
If you have perps on both sides everything is a closed subspace by default, hence Cauchy sequences and the like are irrelevant.
You can't prove this by routing through [math]U \cap W \supseteq ( U ^ \perp + W ^ \perp ) ^ {\perp} \implies (U^\perp + W^\perp)^{\perp \perp} \supseteq (U \cap W)^\perp[/math], since that would let you prove that [math]U \supseteq U^{ \perp \perp }[/math], which isn't true for infinite-dimensional spaces, but I'm pretty sure it's still doable, even if it sucks and you have to expand everything to basic definitions.

Why the fuck does coffee make me sleepy?
I'm literally about to pass out right now
I hope to see an answer when I wake up, this is crazy.

>>15563956
Everyone's natural tendency is to strengthen the statement into "even numbers are paired with vowels and odd numbers are paired with consonants." Formal logic where you limit how much a statement implies is pretty unnatural to most people and requires a more careful reading even for those who are aware of it.

>>15564616
Do you have adhd?

I saw a video about ten years ago about antipodal points on the earth having the same three properties. There are plenty of proofs available that show that there will always be at least one pair of points on the earth exactly opposite each other with the same temperature, but the proof I'm looking for claimed there will always be a pair with the same temperature, humidity, and another property (I think he used altitude, but it could have been almost anything).
I'm questioning this now because I saw this video so long ago I might have just been young and dumb and believed it to be true without really understanding it. His proof went something like:
>The temperature relationship applies not only to spheres but to any circle we draw on the sphere.
>You can draw three circles at 90° angles from each other, using different properties.
>Something something, there will always be at least one pair of antipodal points with the same three properties.
I can't find the video now which makes me think it might have been proven wrong and he deleted it, but what I'm searching for is wordy as shit and youtube's search engine is garbage now so it's probably just getting buried because of their algorithm (half of my search results are about climate change). I obviously don't need the exact video, just a similar proof, but it was probably from numberphile or one of their personal channels.

>>15564616
I don't know the first thing about biology, but from personal experience if you're hyper caffeinated and lacking sleep your body will compensate and try to knock you out. I'm convinced it will do this preemptively in response to the caffeine intake. I got over this by limiting myself to green tea (I highly recommend one with L-theanine if you're interested), but now I have a regular sleep schedule from midnight to 0700 with a 20 minute nap around 1200 and hyper caffeinating is not an issue for me anymore.

>>15564659
Interesting question. I just thought about this now.

Define a function on the sphere which is the difference of a quantity from its antipodal point. Zero values are where the quantity is the same, and clearly there must be some zeros since every positive value implies a negative value on the other end of the sphere. In fact the zeros must form a great circle. Any two great circles intersect so you can extend it to two real values too. But you can easily pick a third great circle that does not cross the pair of antipodal points where the previous two great circles intersected, so I think he is wrong.

>>15564659
Also I think the existence of at least one pair of antipodal points with the same values of two real quantities has something to do with the "hairy ball theorem" so you do not need the perfectly round sphere geometry, it is topological.

>>15564659
I just realized I wasn't clear. He took those circles and rotated them while tracking the antipodal points with the same value and this drew irregular bands around the sphere. After repeating this three times he proved that all three kinds of those irregular bands would overlap at at least one pair of antipodal points.

>>15564683
>>15564693
Yes! I think that's how he proved it actually, I remember seeing a bunch of zeros plotted on a sphere. Two properties would work but I don't see how the third would necessarily have to be true. He used a sphere because he was using the earth as an example, and for simplicity I assume. That's why I think he used altitude as the third by pretending cliffs don't exist, or by smoothing the values to a local average.
I'm just happy I got my point across man. I felt insane trying to describe something I don't understand.

>>15564707
Yeah he's definitely wrong about it holding for three distinct properties though. Three real quantities on the sphere is basically a three-dimensional vector field on a sphere. If you pick the vector field proportional to the radial vector of the sphere that gives an explicit example where there are no antipodal points that are the same. Interesting thing to think about, thanks.

>>15564659
That sounds like a super strong made up version of Borsuk-Ulam.

>>15564659
After holding a globe in my hands for all of one second I realized the map I made is horrendously wrong.

>>15564717
My educational background is almost non-existent and what math I know is mostly limited to what I need to know for electrical
engineering (I was actually thinking about Kirchhoff's voltage law when I remembered this), so I'm not really following you but I'm glad you got something out of it. I'll brush up on vector fields to better understand what you're saying.
But what I think you're saying is, the radial vector will be a unique value at every point of the sphere, like a co-ordinate system, so it couldn't possibly work. But the claim isn't that it will work for any property, only many of them.

>>15564783
>Borsuk-Ulam
That seems like the exact term I needed to search for. Thank You.

>>15564659
>if you're hyper caffeinated and lacking sleep your body will compensate and try to knock you out
By what mechanism could you possibly override adenosine receptors?

>>15564850
>I don't know the first thing about biology,
I have no idea, but if you are experiencing it then it's probably a possibility.

Are dehumidifiers enough to help you survive lethal wet-bulb temperatures?

If so, are passive dehumidifiers effective enough to earn a place in a tropical survival kit? Bonus points for free potable water

>>15565096
Why wouldn't you just use air-con instead? That works at all temperatures and humidity levels.

>>15565172
I didn't say anything about air-con

I have Two stupid questions

1. Why cant microwaves cause cancer?

2. How can microwaves create electrical arcs in on the prongs of metallic forks?

>>15565218
1) Too low energy. Gamma radiation is something like 8 orders of magnitude higher in frequency / energy.

2) I'm not familiar with this phenomenon but if they really do arc then it is likely because the potential will be highest at the tips, high enough to arc.

>>15565239
i think i figured out number 2.

Microwaves can create changing electric/magnetic fields which would induce a current in the metal, then its as you say the potential is at the tips

Another /sqt/, please

>>15564648
Just woke up from passing out
I don't know if I have ADHD I think it's just made up shit so white women can get meth and give their children meth
>>15564659
I will try green tea I guess

I'm trying use a Kolmogorov-Smirnov test to check if my data is normal. Histograms show very not normal data, so I'm expecting the the test to agree with this observation. Using kstest from scipy, (https://docs.scipy.org/doc/scipy/reference/generated/scipy.stats.kstest.html)), if you want to compare your data to a bog standard distribution, you can simply name it as a string. So the syntax is stats.kstest(your_sample, 'norm'). 'norm' is going to be standard normal, i.e. mean = 0 std = 1. My question is this: should I standardize my data first before putting it in the test? If I don't, the test comes back with a p_value of 0. If I do, it comes back with a high p_value well above my level of significance.

Pic related illustrates the point in the question. I make a random sample from a normal distribution with mean 50 and std 6.7. It fails the kstest, it's clearly not from the same distribution as the standard normal distribution ('norm'). But if I standardize that same sample, it comes back with a high p_value: i.e. we cannot reject the null hypothesis of the kstest which states that the sample and 'norm' do come from the same distribution. Like I said earlier, the histograms for the actual data are super not normal. But if I standardize my data, it passes the kstest which suggests that the data IS normal.

>>15564353
Guess the best I can do is make one plot of Re or Abs and Im or Arg of f(z,w) at a time with a 3d plot + color for 3 of the 4 variables while varying the last one separately. Don't think it's gonna be too useful.

>>15564021
are you retarded or trolling. I f you flip the 7, and E was on the other side, then the rule would be disporven

>>15564616
you're getting too much caffeine or trying to stay awake for too long. you need to stay healthy in general, drink plenty of water, take vitamin d3, multivitamin (e.g. a vitamin B12 deficit can kill your energy levels and you can have a deficit even if you eat meat)

and try not to spike your blood sugar too much, i tend to get btfo when i drink a lot of milk or eat hamburgers with huge buns, chicken can make you sleepy too

>>15565658
I never try caffeine because it never works but I'm always tired all the time
I'll sleep 8hrs have a cup of coffee and sleep for 8 more hours

>>15565288
Well, if you decide you want to try legal meth, make sure to mention that, cause paradoxical response to stimulants is one of the symptoms of adhd. It's not a guarantee, but it'll increase your chances of getting a diagnosis.

>>15565763
Maybe I move to Mexico, heard they're easier to get there