/sci/ - Science & Math

Why does [math]\frac{\partial\rho}{\partial t}=0[/math] in magnetostatics?

>>9422480
I like to think as follows:
Consider the Maxwell's equations. The static case, the one that leads us to electrostatics and magnetostatics regimes, can be defined in such a way that the electric and magnetic field does not evolve with time, i.e.

[math] \frac{\del}{\del t} \mathbf{E} = 0 [/math]

[math] \frac{\del}{\del t} \mathbf{B} = 0 [/math]

In this case, the Maxwell's equations read

[math] \mathbf{\nabla \cdot} \mathbf{B} = 0 [/math]
[math] \mathbf{\nabla \times} \mathbf{B} = \mu_{0} \mathbf{J} [/math]
[math] \mathbf{\nabla \cdot} \mathbf{E} = \frac{\rho}{\epsilon_{0}} [/math]
[math] \mathbf{\nabla \times} \mathbf{E} = 0[/math]

Taking the time derivative (partial) of the third eq. above, we have (i think you know some vector calculus, and why the manipulations below are valid)

[math] \frac{\del}{\del t} (\mathbf{\nabla \cdot} \mathbf{E}) = \mathbf{\nabla \cdot} (\frac{\del}{\del t} \mathbf{E}) = \frac{1}{\epsilon_{0}} \frac{\del \rho}{\del t} [/math]

Since we're in the static electromagnetic field case,

[math] 0 = \frac{1}{\epsilon_{0}} \frac{\del \rho}{\del t} [/math]

Therefore,

[math] 0 = \frac{\del \rho}{\del t} [/math]

>>9422497
Sorry, forgot it was $\partial$.
I'm used to packages kappa

Is it worth getting an AS in electrical engineering if I want to get a BS in computer engineering?

Puttus Chromosomus Bagus

>>9422661
I should add, the reason I'm considering doing this is because I want something to fall back on if I realize I'm too much of a brainlet to complete the degree.

>>9422480
because 'statics' implies steady state i.e. partial derivative with respect to time of any function equals zero, duh

Why does hot water clean better than cold water?

Sorry in advance for not using [math] tags but I'm feeling kind of lazy.

If we had some propositional function (not v1 or v2) if and only if (v1 implies v2), what would it be in DNF?

I got (v1 and v2) or (v1 and not v2) or (not v1 and v2) or (not v1 and not v2) from a truth table. Is this correct or am I way off base?

>>9422771
warm water has a higher solubility product. it's more reactive.

>>9422771
Greater kinetic activity makes it easier to remove dirt or grease or whatever, and the higher temperature kills more bacteria.

Can a nuetron decay into a proton?

If 2 wire , A1 and A2 with opposite current direction is coincide to one another, will the resultant magnetic field cancel out each other?

Suppose that the current on A1 is higher, , do I just have to draw the magnetic field of A1 considering A1>A2?

Do people consider me stupid despite that I learn computer programming and other kind of knowledge through Lynda.com?

When I'm minimizing a DFA using the table filling method, should I include the dead state on the table?
Because when i include it, in the end it gives me a pair between the dead state and the starting state, which doesn't make sense. (and also ruins my DFA's function)

>>9423099
Absolutely

How to gitgud at calc 2? I struggled with the introduction of Integrals in Calc 1 and we’re starting pretty quickly in Calc 2. I would like to be able to see a integration problem like
Integral[sqrt(25-x^2)]dx and be able to understand the way to get the answer 25pi/2. Introduction of trig and all is just blowing my mind. What can I do?

if I were to continually breed short people contiually to get shorter people, would they be healthy, or would they have simmilar issues that people with dwarfism have?

>>9423592
Practice
In math everything boils down to practice

Is a nuclear plant really that big of a risk this day and age? If it produces clean energy, why aren't there more of them?

>>9423632
they would be healthy

as healthy as a chihuahua dog
frightened and shivering all the time
also cute

>>9423592
It really comes down to memorization.
If you see things with square roots and [math]x^{2}[/math], it usually implies arctrig integrals.

when looking at [math]\int \sqrt{25-x^{2}} \;
\mathrm{d} x[/math] we recognize the arcsin function (I've added the picture as a resource) where [math]a^{2}[/math] is 25, meaning a is 5.

This means the integral is [math]arcsin\left ( \frac{x}{5} \right ) + \mathrm{C}[/math]

>>9423676
>>9423592
whoops forgot the picture

Is Algebra by Shen-Gelfand a good book?

>>9423937
>Is Algebra by Shen-Gelfand a good book?
Why don't you read it and find out?

How do I know when to use a bar graph or line graph?

how can i figure out what wavelengths of light would be scattered by a molecule, given IR and Raman spectra?

e.g. The Raman spectrum of XeF4 shows bands at 161, 291 and 586 cm–1, whilst
in the IR spectrum bands are observed at 218, 524 and 554 cm–1. Calculate the wavelengths of light scattered by a sample of XeF4 when it is illuminated by a HeNe laser (632.81 nm).

is it just the wavelengths of light that correspond to the difference in wavenumbers for the Raman spectra?

On Earth there's relatively catastrophic events like earthquakes, tsunamis, etc.

Are there analogs on the universal scale, something that greatly disturbs a massive area of space? I don't mean things like black holes since they're more 'permanent'

if p<q them being primes is it posible that q divides p^2-1?

>>9424064
p=2 q=3

>>9424068
O shit, yea asuuming both primes are odd.

>>9422464
>Homo neanderthalen/sci/s
plural Homo neardenthalen/sci/

>>9424070
>O shit, yea asuuming both primes are odd.
No:

Assume q divides p^2-1.

Since p^2-1=(p+1)(p-1) and q is prime, q either divides p+1 or p-1.

Since p<q, q can't divide p-1, so q divides p+1.

So q<=p+1.

So p<q<=p+1 implies q=p+1 which is even.

are scalars just 1x1 matrices?

we like stupid questions here

https://discord gg/c37NwyB

>>9424084
>are scalars just 1x1 matrices?
https://math.stackexchange.com/questions/65002/are-one-by-one-matrices-equivalent-to-scalars

>>9424083
Fuck, I was starting to look with primality tests and shit and it was just basic algebra... thnx bro.

by what process do you get to use these symbols
>>9422497
and where can i learn how to use it

also what does TEX mean on top of the reply window?

>>9423965
a bar graph is used when you want to compare data between several different sources, like cities, bank accounts, or whatever else.

a line graph is used when you have a single measurement, with one independent and one dependent variable, like money and time, or jews vs days, or even how many cookies a bakery makes vs hours its open.

>>9422480
>Magnetostatics is the study of magnetic fields in systems where the currents are steady (not changing with time). It is the magnetic analogue of electrostatics, where the charges are stationary

Because ideal constant current sources aren't real so you'll never have one indefinitely charging a capacitor. In real life it will hit it's max supply voltage and the current will taper off.

>>9423653
If you do it properly no, it's hardly a risk, but that implies anyone will finance a money sink without cutting corners.

What's the difference between mass and weight ?

I'm pretty sure mass is just the quantity of "matter" in it and is therefore static for a given object
My friend argue that within a system with 0 gravity or force pushing it, the mass of an object become 0
Which one is it ?

>>9424474
mass is a way to quantify how resistant you are to changes in force, which is why it's sometimes called a measure of inertia (e.g. moment of inertia)

the mass is intrinsic and a property of matter, so what you're made of determines your mass

weight is the measurement of how much force there is between you and whatever planet you're on, so when we talk about weight here we're talking about Gm1m2/r^2 where r is the radius of the earth and m1 is the mass of the earth (and G is the gravitational constant)

so a system with 0 gravity means 0 weight, not 0 mass

also you have to be underageb& to not already know this

>>9424497
Thanks, also I'm 28 so not exactly underage

>>9423653
The biggest obstacle is that they're incredibly expensive, and are potentially a high-risk investment (they'd be prohibitively high-risk in a free market, but that isn't the issue; no-one builds them nowadays unless the government legislates to provide some guarantee of future income).

Also, you have no idea what the clean-up costs are going to be like in 30-50 years time (the licensing process revolves around making damn sure you can't just fold the business once the reactor reaches end-of-life and the future consists of all costs and no income).

Suppose [math]H(t)=\left(H_{ij}(t)\right)[/math] is a square matrix. How does [math]\frac{d}{dt}[/math] operate on [math]H[/math]?

>>9424659
Are you looking for an answer other than coordinate-wise?

>>9424662
Are you saying the differential operator is treated like a scalar and distributed to all of the elements of the matrix?

>>9424666
>Are you saying the differential operator is treated like a scalar and distributed to all of the elements of the matrix?
Are you looking for a different answer?

What is honestly the difference between an [math]n\times 1[/math] matrix and a vector? Why even call it a column vector if it's not exactly the same thing?

>>9424696
>What is honestly the difference between an n×1 matrix and a vector?
A vector is an element of a vector space.

An nx1 matrix is an ordered n-tuple

>>9424696
For example, consider the 3 dimensional vector space of polynomials with real coefficients and degree at most 2

Then 1+3x is a vector, but its '3x1 matrix representation' with the basis 1,x,x^2 is [1,3,0]

>>9424711
OOOOOOH so the column vector is just the coordinate of the vector?

>>9423937
Yes.

Assuming one day we can made really fast spaceships, would weird relativistic effects harm the human body if we went fast enough?

This board is useless waste of space.

>>9424786
>This board is useless waste of space.

>>9424798
Haven't you got a white supremacy thread to bump?

>>9424819
>Haven't you got a white supremacy thread to bump?
Are you okay?

>>9424823
Doing better than you by the look of things.
What's wrong with this place?
Why are you guys so fucking weak?

>>9424827
>Why are you guys so fucking weak?
I'm not a "guy".

>>9424827
>Doing better than you by the look of things.
Your delusions of white supremacy threads indicate otherwise.

>>9424830
I'm sorry, maybe my description wasn't precise enough.

Should I just call it a nigger hate thread?

>>9424829
Sorry I misgendered you. Tits of GTFO.

>>9424835
>nigger
Why the racism?

>>9424836
That is what they are called in their homeland.

>>9424836
Why the racist shitposting every day?

Why do /sci/ put up with it?

>>9424836
Come on now.
You seemed so brave a minute ago.
Why so quite all of the sudden?

>>9424829
Why are you so fucking weak?

What's wrong with you /sci/?

>>9424841
>Why so quite all of the sudden?
Just pretending to be retarded I expect.
They're probably laughing that the joke's on you for replying.

>>9424849
They are /pol/tards?

>>9424857
Worse, they are cucked by poltards.

You can literally do anything you want to /sci/ and they will take it.

Some will even thank you.

For the challenge question, what I did was
[eqn]\frac{n_{1}}{4}+\frac{n_{2}}{8}=5-n_{1}(p-\frac{1}{4})-n_{2}(q-\frac{1}{8})[/eqn], by making n2=2 I get [eqn]n_{1}=\frac{5-2q}{p}[/eqn]. The solution given in the book is 1/2, but it could as easily be 2/1 by making p=1, q=1/2.
Is the book wrong or did I make a mistake somewhere?

>>9424932
Forgot the picture.

>>9424096
dumb answer

>>9424084
Scalars form a 1D vector space and so do 1x1 matrices. So they are isomorphic and you can essentially do anything you can with one with the other.

>>9422662
Just balls deep Electrical Engineering with Computer Engineering, I'm in a major that's less related to EE and my average semester still floats around 16-18 credit hours.
t. EE and MatSci student

>>9424084
They are isomorphic.

>>9424696
They are isomorphic.
[math] V^* \cong V [/math]
One is a linear functional, the other one is a vector.

>>9424840
>Why do /sci/ put up with it?

There is a report function. There is a hide function.

why are improper fractions improper?
i understand why they are, the numerator being larger than the denominator, i just don't get how that makes them improper.

>>9425291
They are not improper. Nobody uses that term for fractions except like retarded teachers in elementary schools.
The only thing that you might consider "improper" about a fraction a/b is when gcd(a,b)=/=1.

>>9424994
>So they are isomorphic and you can essentially do anything you can with one with the other.
You can multiply any matrix by a scalar, you can't multiply any matrix by a 1x1 matrix.

>>9424840
>Why the racist shitposting every day?
I don't know; ask yourself why you're abusing racial slurs on a science and math board.

>>9424842
>Why are you so fucking weak?
Do you really need to swear? It invalidates your post.

it says this is wrong.

am i retarded? this isn't for marks.

>>9422464
What forces will be acting on a ping-pong ball at the exact moment it touches the ground?

We have that $X_1, \dots, X_n, \dots $ are iid random variables with $X_i \equiv X$ for all $i$, where $X$ is absolutely integrable.
Define $S_n = X_1 + \dots + X_n$ where $X_i, 1 \le i \le n$ are random variables.

Tao states this sparsification Trick:

> Next, we apply a sparsification trick. Let ${0 < \epsilon < 1}.$ Suppose
that we knew that, almost surely, ${S_{n_m}/{n_m}}$ converged to ${{\bf
E} X}$ for ${n=n_m}$ of the form ${n_m := \lfloor (1+\epsilon)^m \rfloor}$
for some integer ${m}$. Then, for all other values of ${n}$, we see that
asymptotically, ${S_n/n}$ can only fluctuate by a multiplicative factor
of ${1+O(\epsilon)}$, thanks to the monotone nature of ${S_n}$. Because of
this and countable additivity, we see that it suffices to show that
${S_{n_m}/{n_m}}$ converges to ${{\bf E} X}$. Actually, it will be enough
to show that almost surely, one has ${|S_{n_m}/{n_m} - {\bf E} X| \leq
\epsilon}$ for all but finitely many ${m}$.

Why can $S_n /n$ asymptotically only fluctuate by a multiplicative factor of $1 + O( \epsilon)$ ?

Is it orgo or ochem or organic?

What is the difference between taking a derivative of a limit and of a function? In what way are those two different? I always thought that you only take derivatives of functions to get a derived function that gives slope at each point of the graph of the function we derived from...

When doing implicit derivation, why are we doing what we're doing? I can't seem to find an explanation on the internet. Why do we derive x normally, and y has to be multiplied by dy/dx specifically? What if I had other symbols? What's the reasoning behind it? In school we haven't used dy/dx or d/dx or any Leibniz notation whatsoever ONCE, then all of a sudden, BOOM class, I'm just gonna put this dy/dx here outta fucking nowhere, without even explaining what Leibniz notation IS (we only ever used y and y', but suddenly a wild d/dx dy/dx appears), because fuck you that's why.

I WANNA KNOW WHY I DO THE SHIT THAT I DO, I DON'T WANNA PLUG AND CHUG LIKE A MONKEY!!

>>9425661
All you need to know additionally to understand it is the pic related and a def o deriviative, as a slope of the tangent of the curve at a given point.

>>9425661
>I DON'T WANNA PLUG AND CHUG LIKE A MONKEY
The topic you're """"studying"""" requires it, since only monkeys use it.

>>9422464
>Taylor sequences
So, looking at the definitions, the part I do not get how you can deduce from the inequality above theese two integrals? I get from where the inequality comes from (absolute value), I know the rest of the proof when we follow with the integrals, but how would you know that integrating in this way would be the next step? Is it just a "lucky shot" or is there an explaination in baby steps that connects it with the inequality above?

>>9425661
see >>9425693
calculus and algebra are the most bullshit, counter-intuitive areas of mathematics, you'll have to accept the fact that you are forced to be a monkey while working with them

>>9425712
>calculus
>area of mathematics
>caring about """intuition"""
You are one of the monkeys I was talking about.
>algebra
I doubt you have studied even the basics of it.

how does everyone think about classical entropy, im happy with microstates, but i cant fathom an extensive, measurable quantity that has no physical meaning other than a vague notion of 'the dispersal of or avaliable energy'

>>9425777
>entropy
No such thing.

>>9425811
whats dG/dT then?

Did I get it right?

>>9425830
[math]\sqrt{10}[/math] is not well-defined in the first place, so no.

>>9425696
> but how would you know that integrating in this way would be the next step? Is it just a "lucky shot" or is there an explaination in baby steps that connects it with the inequality above?
The only thing being used here is the fundamental theorem of calculus.

>>9425830
What do you need to add to 9 (which is just 3^2) to get 121 (which is just (7+4)^2)? Then take both the positive and the negative square roots and you have your answer.

>>9425830
3^2 =/= 9^2, also plug your values back in to check

>>9425400
Did you try 17.49? There are some different conventions for statistics, might be that the lower bound is excluded and the upper bound included, i.e. (17.49,18.74] (though I personally only saw it the other way around), this deals with values between 17.49 and 17.50 (but then obviously the question does not make sense)

Otherwise, try the two other numbers and just assume it is an error

>>9425864
>thinks negative square roots exist

Is molecular biology just all wrote memorization, and there isn't really any patterns to figuring it out?

>>9425884
>thinks arbitrary positive square roots exist

>>9425830
11^2 - 9^2 = 40 ??
also, aren't you too young for this board?

>>9425906
>11^2 - 9^2 = 40 ??
t. brainlet

>>9422464

Can someone just tell me if I understand this correctly, so a function is a mathematical expression that relates two variables and allows us to see the relation they are in. Now a derivative of a function would be a new function that allows us to see how fast one variable changes in relation to the other at a certain point.

>>9425971
>so a function is a mathematical expression that relates two variables and allows us to see the relation they are in.
No.
https://en.wikipedia.org/wiki/Function_(mathematics)#Definition

>>9422661
>AS in electrical engineering

Community college degrees are worthless. The courses you take are closer to EET monkey work.

>>9425971
you're kinda hinting at implicit functions and the implicit function theorem there

What's a good beginner text on real analysis? I've only done calc i and ii so from the sounds of it Rudin wouldn't be suited for a brainlet like me.

whats the pop on gummys? who only shows 49

>>9426075
>good
>real analysis
No such thing exists.

>>9426175
Wrong board/thread friendo. And I believe he caps it at 50 pop because he's running the server from his mom's basement ;^)

>>9426209
oop, and its way more than 50. possibly 100

>>9426075
Abbott is good and easier then rudin

Can you eat rape?

>>9426528
apparently so
http://www.princesstafadzwa.com/sauteed-rape-canola-greens/

Didn't get into the uni I grew up idolizing
After a full semester at the next-best school I don't feel any better about it
Does it ever go away

How many hours do some of you study? I try to study around 45-50 hours a week but I get lazy and do either 10 or 20 hours a week.

what two numbers add to be 20 and multiply to be -56

>>9426712
x + y = 20
x * y = -56
20 - x = y
x * (20 - x) = -56
x ~ -2.5
-2.5 + y = 20
y = 22.5

y ~ 22.5
x ~ -2.5

>>9426723
>~
cringe

>>9426728
proof by autism just for you

>>9426735
>proof
i don't see a proof in your post.

Im 27. would be 28 going to school.

is it too late for me to try a physics degree? i would want to get at least a masters. am i too old to be going to grad school in my 30s? by the time id be looking for a job, id be 35. thats a little worrying

>>9422464
Can someone explain to me what the question is asking and how the answer is obtained? I've studied plenty of differentiation/ integration though I've yet to see anything like this before. What do I have to study to understand it in full detail?

>>9427068
This isn't just plugging values into dy/dx (once integrated) and finding the result, is it?

>>9426356
thanks

>>9426712
x+y=20
=> y=20-x
x*y=-56
=> x*(20-x)=-56
=> x^2-20x-56=0
=> x=(20±sqrt(400+224))/2
= 10±sqrt(156)
(10+sqrt(156))+(10-sqrt(156))=20
(10+sqrt(156))*(10-sqrt(156))=100-156=-56
NB:
sqrt(156) = 12.4899959967968
10+sqrt(156) = 22.4899959967968
10-sqrt(156) = -2.4899959967968
The 9's aren't rounding error; 1249^2 = 1560001.

>>9427139
>sqrt(156) = 12.4899959967968
Wrong.

>>9427068
Is that from some numerics course?
Try using Euler method

brainlet here

So, what's the answer, /sci/?

>>9427195
What does CpdT= ?

What do I major in if I want to eat?

>>9427204
>What does CpdT= ?
sorry what i don't get it

A geologist finds that the buoyant force on a 9.50-kg rock is 29.5 N when submerged in water.

a. Find the weight of the rock when submerged in water.

b. Find the density of the rock.

I know you're supposed to use B = p V g, but i'm not exactly sure what the values for the variables should be

How do I put t (time) on the left fucking side with everything else on the tight?

>>9427327
quadratic formula

What the fuck does an atom look like?
All the pictures I can find are just 3d spheres or renderings of electron clouds. I know you can't take a picture of one but there has to be an artists rendering that doesn't look like some newfags class project on /3/

>>9427342

>>9427413
>Plum pudding model

>>9422464
Will America honestly make it to Mars by or before 2024? I would like anhinest answer.

>>9427342

just look at ur dick

>>9427454
Doubt it. By the time we get a plan finalized, the next president will just scrap it, and even if we do get a plan in place it will take a lot longer to actually act.

>>9427333
can you do it?

>>9427518
[math] \frac{a}{2}t^2 + \textrm{v}_it = d \\\
a^2t^2+2a\textrm{v}_it = 2ad \\\
a^2t^2+2a\textrm{v}_it+\textrm{v}_i^2= \textrm{v}_i^2+2ad \\\
(at+\textrm{v}_i)^2=\textrm{v}_i+2ad \\\
at+\textrm{v}_i=\pm\sqrt{\textrm{v}_i+2ad} \\\
t=\frac{-\textrm{v}_i \pm \sqrt{\textrm{v}_i^2+2ad}}{a} [/math]

>>9427589
forgot the square with two v_i terms, but you get the point

Does anyone have a link to a proof that [math] L^p[a,b] [/math] is complete?

>>9427729
Let [math] f_n [/math] be a Cauchy sequence of [math] L^p[a,b] [/math] , i.e. :
[math] \forall \varepsilon >0 : \exists N : \forall n : n,m \geq N \implies \int_a^b |f_n(x) - f_m(x)|^p dx < \varepsilon [/math] .

What I am struggling with is how the fuck does one find Where it converges?

>>9427729
Any functional analysis book. For eg. Lang

>>9427342
>I know you can't take a picture of one
https://en.wikipedia.org/wiki/IBM_(atoms)

>>9427729
I have proven this in like 3 different classes, still don't remember it.

>>9427342
No one knows what they actually "look" like.

>renderings of electron clouds

This is the best you're gonna get.

what happened here?

>>9427882
They just used exponents instead of radical, haven't actually done anything yet.

Why wouldn't an intrauterine formulation of progesterone cause amennorhea?

Surely having a shit ton of progesterone around the endometrium would keep it ripe/prevent it from shedding.

>>9427898
oh ok so they just did 8x^2 * x ^ -1/2
4/2 - 1/2 = 3/2

>>9423187
Yes, this is how coaxial cables cancel inductance for high frequency

Any suggestions for part a? I tried (12P3)*(12C3)*(12C6) to get the answer 268329600, but that's obviously incorrect.

I'm probably going to major in EE or CS
the problem is I stopped at Algebra II in Highschool.
From what I can tell, Precalculus, Trigonometry, Physics I and II, and Calculus I and II are all prerequisites to just begin either degree.
Right now I'm in my second semester of eight for a bachelor's, I'm afraid to ask, but does this mean I probably won't be getting the degree in just 4 years?

>>9428088
You probably can if you're willing to take summer school

>>9428088
No it means that you will have to spend 1-2 months studying that basic shit before you start.

>>9428099
What do you mean 1-2 months? Don't I need to take the full semester courses for the credit (not counting summer school)? I'm not good enough to CLEP out of math courses, but I can do well enough with the semester long courses

>>9428096
from what I've heard, precalc and trig aren't the most difficult so I might, *might* be able to knock them both out in one semester. That'll still leave me with the physics and calculus courses.

I just don't see how it's possible for me to complete the major in 4 years.

Maybe I'm just not reading this flowchart right, or I'm misunderstanding something

This might sound like a meme question, or just a really stupid one, but how does magnetism actually work?
It works in space right?
As in, you can put a magnet in a near perfect vacuum, and it will still suck metal towards it.

How does it do that? If there is literally no matter between the magnet and the metal (since its all in a vacuum) how does it work?
What is the actual "things" that makes magnetism work? Is it some sort of radiation? Or some dark matter bullshit?
I've heard people say "magnetism works by pushing and pulling electrons" but if it's in space that can't be true, can it? There are virtually no matter between the magnet and the metal in space.

>>9428107
Don't really understand that flowchart either, you should probably just setup a meeting with your department's academic advisor. In my experience they've been pretty helpful.

I'm considering changing from biological sciences to Chemical and Biological Engineering. I have been in a ChemE / BioE lab for the last two years and I really enjoy it. I want to get my PhD in bioengineering, however a lot of the places require an engineering degree for the bioengineering degree. Should I take the extra two years to do the chemE or just finish the biological sciences degree.

>>9428172
chemE

>>9428113
No one knows how magnetism works at a fundamental level. Havent discovered that yet.

My personal theory is that magnets act as a filter for some fundamental particle. So magnets should be weaker in space because theres less stuff running around to be filtered.

We havent actually gotten a conclusive test yet to know how magnets operate in space. Others will claim they work the same as earth.

>>9428192
Alright, thanks. I thought everyone knew exactly how magnets works and I was just out of the loop.
Good to know I'm not that uninformed!

what's an easy thesis subject on numerical analysis or statistics or machine learning for an undergrad. im tired of school

how do I verify that the set {x∈ R : 4 ≤x < 8} contains an ε-neighborhood of the number 5.

How come STEM majors are highly touted but Finance and Accounting majors are nowhere to be found in advertisements?

>>9428745
What do you mean?

>>9428597
Pick epsilon smaller than 5-4

>>9423652
This.
>>9423676
>memorization
Absolutely NOT this.
Find sites or textbooks to practice out of. I suggest Paul's Online Math Notes.

>>9426784
Literally never too late my guy
unless you're dead

>>9426784
No, if anything you'll get more respect from the professor's. There was a guy at my school who started at age 30 in physics department and is now a PhD at a top 10. Is also NSF GRF winner.

>>9428811

Like Governments and organizations going to school and advertising STEM degrees, but Accounting and Finance are nowhere to be found.

>>9422464
how do i calculate the reaction rate in m/dm^3 of iron and HCl by measuring volume of H2 gas created

>>9422464
How accurate is this image?

I'm going back to school after 10 years (engineering) so I'm relearning math. Right now I'm reading Basic Mathematics. The idea is I take the assessment test and hopefully get placed into Calc 1 so I don't have to take trig or algebra. I'm too old to waste time now. What do you recommend after Basic Mathematics?

If time ceased to exist, did time ever exist?

>>9429125
Gelfand books are good for forcing you to understand what's going on rather than "plugging the problem's numbers into the given worked example and working out the differences in arithmetic" mindless approach poor students gravitate to to their peril. If you mastered the material already, you should be able to breeze through them over a few days.

Lang's Basic Mathematics is an okay 'rigorous' precalculus book.

A reading a proof book and digesting it is like cheat code that makes future math courses easier to understand. But you don't have to learn it right now if you don't want to or don't have time.

The students that do the best on placement exams tend to already have studied a little bit of calculus and gotten a lot of practice with the precalculus topics in the context of calculus. If you want to study ahead then I recommend reading Lang, Simmons, or Hamming's book.

The rest of the chart is a mess and you should ignore it.

>>9422464
Did some vulcanizaiton of rubber. Mass of the output material was larger than the mass of the input material. What went wrong?

>>9428745
Which country are you talking about? Back in home, Kebabistan, social sciences are widely advertised. So, I guess you are referring to a specific country.

>>9428113
>>9428192
Isn't it related to spin?

>>9428113
The permittivity and permeability of vacuum are close to those of air, so it doesn't really make a difference whether they are in vacuum or air.

>>9428113
https://www.youtube.com/watch?v=hFAOXdXZ5TM
there is no empty space, fields are everywhere

Suppose I want to do a standard, one-sample t-test. In which situations, if at all, do I use Bessel's correction for the variance estimator? Why do some authors seem to use it while others do not?

>>9429251
>Bessel's correction
When dealing with sample you go for n-1, when dealing with population you go for n. That's dumbed down explanation.

Is it too late for me ? I'm 22 and I've recently taken an interest in mathematics and astronomy, but the most advanced maths I've done is algebra. Should I just bin this as a hobby or would I be able to dive deep into subjects after a year or two of freshing up my math knowledge?

>>9429283
>be me
>have a finance degree
>life goes sideways, my plans are all screwed
>fuck this ima go study something epic
>get in applied physics at the age of 23
>about to finish now at the age of 26-27

Hardest part wasn't the content of the courses, but finding the money to sustain average living standards while excelling in all courses.

I'm about to go to college soon. Is going for a BS in ME then getting a Master's in Aeronautics a good idea? My country (Flipland) doesn't have much in Aeronautics/Aerospace and maybe an BS in ME could help when I try and go off seas

If you have a 3x3 matrix, won't each column vector represent a plane each?
Apparently they form a line but I don't know how that works.

any bio majors here?

is this a template strand or a coding strand? and can you give me an explanation too

>>9429283
It was over when you hit 14 dude, almost everyone in math programs started when they were 10

>>9428837
Studies have shown that cognitive ability starts a downward trend after 25. I would be blown away if a 30 year old could actually start a career in physics

>>9429498
50

How the fuck is he getting this? I'm getting totally different results.

>>9429593
Have you considered that you're doing it wrong?

>>9429613
Yes and that's why I'm asking how he got to those numbers.

>>9429593
>I'm getting totally different results.
How are we supposed to show you what you're doing wrong if we don't know what you're doing?

>>9429195
>If you want to study ahead then I recommend reading Lang, Simmons, or Hamming's book.
Lang is a meme.

In Riesz's Representation Theorem's proof, how does one come up with the expression in red in the pic?
It seems arbitrary to me, but there has to be some reasoning...

>>9422464
How do I get
100x^3/(x+1)^4
From
3log x -4log(x-1) + 2

Sitting here ~15min already with it

>>9429917
Use your log rules:
alog(b)=log(b^a)
log(a)+log(b)=log(ab)
log(a)-log(b)=log(a/b)
and the fact that
2=log(100)

>>9429929
>>9429917
also your 100x^3/(x+1)^4 should be in a log

Given [math]f(x,y,z)=0[/math], show [math]\left ( \frac{\partial x}{\partial y} \right )_{z}\left ( \frac{\partial y}{\partial z} \right )_{x}\left ( \frac{\partial z}{\partial x} \right )_{y}=-1[/math]

I tried finding the formal partial derivatives and solving for each term, but I just get 0.

>>9429929
Thank you kind anon.
x^3/(x+1)^4 = k
k+2
would be alright, right?

>>9429951
>I tried finding the formal partial derivatives and solving for each term, but I just get 0.
Show your work.

>>9429951
Should the function appear in that expression?

>>9429960
that's a lot to type out
>>9429965
what I wrote is what's given

I'm not sure where the function being zero comes into play

>>9429951
>Given f(x,y,z)=0, show (∂x∂y)z(∂y∂z)x(∂z∂x)y=−1
That's not true.

>>9430005
it's exactly what's in the textbook

>>9430016
>it's exactly what's in the textbook
What's your point?

>>9429915
The codimension of N(f) is 1, so every x can be written as z + v, where f(v) is 0. Assume that |z_0|^2 = f(z_0) so that f(x) = <x, z_0> so that z_0 * f(x) is the projection of x along z_0. Now you can see that v is just the component of x along N(f), up to a multiplicative constant.

Hoping someone can help me with this, since I have no clue how to solve it despite reading up on the undetermined coefficient method.

===This is a probability question. I want the formula or guidance on how the fuck this can be solved as it has been resting on my mind for a while and making me feel dumb.===

An event is positive on average 60% of the time if variable A is present.

The event is also positive on average 55% of the time if variable B is present.

The event will be positive on average 50% of the time when activated and affected by other random variables.

If both variable A and B are present what is the probability of the event being positive?

Is it necessary to to assume any instances of A and B already being present together has not affected their individual odds before answering this?

>I've looked online for a while on any examples of this problem and I couldn't find any...

>>9430126
I think you need either more information on the distributions of A and B or [math]P(X|\bar A,\bar B)[/math].
With the former, use Bayes.
With the latter, draw a Venn.

why are analytic functions important? how are they connected to fourier coefficients? i don't even understand contour integrals help me

>>9425630
OK tier: ochem, organic
Brainlet tier: orgo

>>9430034
you're wrong, the textbook is right. I figured it out and can explain it if anyone wants

>>9430293
>the textbook is right.
It's not.

>>9429485
Coding strand, ATG codes for Met, (AUG in RNA)

>>9430229
I'll consider here analytic functions to converge to their Taylor series everywhere, which is a more strict definition. This kind of analytic function is nice, because
1. they are easy to express,
2. they form a ring,
3. they are trivially easy to derivate and integrate, and derivatives always exist,
4. many functions that you encounter are analytic, most notably linear functions.
I don't think they have much to do with Fourier things, though. You might say that Taylor and Fourier series are similar, but they are just special cases of a more general method that happen to be particularly useful.

>>9430296
You're a stupid faggot, my teacher just showed us how to do it in class. Are you really so hubristic to think that the textbook author, who is a professor at MIT, and my teacher, who has a master's in math are both wrong, and you're right? Fuck off.

>>9430331
>You're a stupid faggot, my teacher just showed us how to do it in class.
Why the homophobia?

>Are you really so hubristic to think that the textbook author, who is a professor at MIT, and my teacher, who has a master's in math are both wrong, and you're right?
Yes, your argument from authority is in fact not an argument.

The textbook remains incorrect.

>>9430368
>The textbook remains incorrect.
Gonna need a source on that one, buddy.

>>9430391
>Gonna need a source on that one, buddy.
No source is needed, there exists no proof of the desired equality given the premise.

>>9430316
can you explain what a residue is or laurent series? i don't understand the diagram in wolfram with the circles

>>9430054
bump

I found a master's program in South Africa for natural resources that I'm interested in. Anyone done graduate work internationally before? How hard was the process to get a visa? How did you like being overseas?

>>9430397
Perhaps that is true, but the burden of proof lies on you. You must demonstrate that the equality is violated, since it was stated as a given and only the proof was requested.

>>9430481
>Perhaps that is true, but the burden of proof lies on you.
As I've already said, no such proof exists since the claim is incorrect. Your 'professor at MIT' and 'teacher with a master's in math' are both sorely mistaken.

>>9429951
What's the subscript supposed to mean?

>>9429951
This follows trivially from the implicit function theorem. I don't know what you fags are arguing about.

>>9430521
>This follows trivially from the implicit function theorem.
Wrong.

>>9430521
>I don't know what you fags are arguing about.
Why the homophobia?

>>9430293
>I figured it out and can explain it if anyone wants
No, you can't.

>>9430525
>>9430527
Nice counterarguments

God, the state of this board

>>9430547
>Nice counterarguments
There's no need for a counterargument since "This follows trivially from the implicit function theorem." is not an argument, simply an incorrect claim.

>>9430525
>>9430525
>>9430527
>>9430537
>>9430547
If you want to be a pedantic faggot (yes I am homophobic) go to reddit (no, this post is not ironic).

>>9430549
It is trivial. What's the expression for the partial derivatives by the implicit function theorem?

>>9430557
>If you want to be a pedantic faggot (yes I am homophobic) go to reddit (no, this post is not ironic).
The question was posted nearly four hours ago and you have yet to provide anything that resembles a "proof" of its validity (which is in fact impossible, since the claim is false).

>>9430564
>What's the expression for the partial derivatives by the implicit function theorem?
Do your own homework.

>>9430567
Why don't you post a counterexample to that statement then

>>9430577
>Why don't you post a counterexample to that statement then
What part of 'do your own homework' went over your head?

>>9430566
If it's false, then how could I possibly provide a proof? You're only proving your own ignorance.

>>9430584
>If it's false, then how could I possibly provide a proof?
I said "proof", not proof. Of course you can't provide a proof but you can perhaps provide a "proof" as per the claim here >>9430331

>>9430583
https://en.wikipedia.org/wiki/Triple_product_rule

>>9430594
Neither of these "proofs" are valid, nor do they claim to be.

>An informal derivation
>this proof makes many implicit assumptions regarding the existence of partial derivatives, the existence of the exact differential dz, the ability to construct a curve in some neighborhood with dz = 0, and the nonzero value of partial derivatives and their reciprocals
>second "proof" assumes invertibility without justification

Next?

>>9430577
>Why don't you post a counterexample to that statement then
Are you braindead? f(x,y,z)=0 is a counterexample.

>>9430621
>>9430617
Stop being a pedantic retard. Assumptions such as non-zero partial derivatives obviously have to be made.

>>9430636
>Assumptions such as non-zero partial derivatives obviously have to be made.
Hence the question is false, so what part of this is confusing you?

>>9430636
>hurr durr obviously f(x,y,z)=0 means you make these 5 other non-trivial assumptions

>>9430681
>"Proove"
Post disregarded.

Why don't you fucking nerds just show you work so we can see who's right or who's just blowing smoke out their ass

>>9430681
None of those steps are justified.

Next?

>>9430681
>writes out all this garbage just to be BTFO

I'm closing 4chan and there's nothing you can do about it.

>>9430696
Thanks bro

>>9430682
Equations such as those are obviously used in the context of implicit equations, so it's completely natural to make those assumptions. In fact, not being able to do that just reveals your inexperience.

>>9430681
If you let f(x,y,z)=0 then your algebraic manipulations fall apart in the third line of your "proof".

>>9430704
>math
>"obviously"
[hand waving intensifies]

>>9429951
this question literally makes no sense

>>9430681
Why the homophobia?

>>9430704
>Equations such as those are obviously used in the context of implicit equations, so it's completely natural to make those assumptions.
There is no justification for making those assumptions.

>>9429951
There must be a typo here, since if f(x,y,z)=0 then the left hand side of the second equation is 0, not -1.

>>9430712
Ok whatever. I'll stop posting now.

>>9430721
>Ok whatever. I'll stop posting now.
Thank you, it's best to refrain from interjecting into conversations that you don't have the mathematical maturity to adequately approach.

>>9427205
Pure Math

Then you can but just one donut, stretch it as big as you want and never run out of donut. Just don’t make a hole in it

what do they mean in higher level math when they say 'is an isomorphism' / isomorphic to. something to do with bijection?

>>9430837
isomorphism = bijection as sets + compatibility of any algebraic operations (homomorphism)

I.e. you could have a bijection from the set of integers to itself like f(x) = x+1, but it's not an isomorphism since the function isn't compatible with addition (the condition f(a+b)=f(a)+f(b)). For example f(a) = -a is an isomorphism since it's a bijection and f(a+b) = -(a+b) = -a + (-b) = f(a) + f(b)

>>9430868
>For example f(a) = -a is an isomorphism since it's a bijection and f(a+b) = -(a+b) = -a + (-b) = f(a) + f(b)
should also note this is an isomorphism of groups

Are there any accessible jobs/careers where I can help contribute to science without having to be intelligent or qualified?

>>9430203
Thanks, I'll look into it. I have the data that indicated that variable A occurs about 30% of the time and variable B about 20%.
I don't know how to do distribution s for this but I guess I'll have to learn.
I'll try that Venn formula when I get to excel or something and see if it spits out something useful and likely.

Thanks for your help. I had been thinking that as the base % was 50% I'd take the percentage differences of the lower difference and add or subtract to the greatest or smallest variable.
Something like
P=A+A*(B-0.50)
0.6+0.6*(0.55-0.50)
0.6+0.033
=0.633
Pretty sure that is not the correct way of doing it but it produces the kind of numbers that looked pretty correct and was easy to do in my head.

>>9430706
No, you fucking retard. The first line references x, y, z as independent variables while the partials in the fraction reference x, y, z as intermediate variables. The two expressions, although notationally the same, are not equal.

>>9431039
>No, you fucking retard. The first line references x, y, z as independent variables while the partials in the fraction reference x, y, z as intermediate variables. The two expressions, although notationally the same, are not equal.
Wrong.

If f(x,y,z)=0 then the algebraic manipulation performed to obtain the third line of the "proof" is invalid.

>>9430884
Drug trails and military are the big ones that come to mind.

>>9429498
Well first, Ive been studying physics and math since I was 18 and didnt have the funding to go to school until now.

Second, I dont believe that is meaningful since most people make poor decisions at a younger age and dont show intelligent thinking until theyre older.

>>9428837
>>9428967
Thanks guys

>>9428228
Yep, physics is still a mystery at the subatomic level and smaller.

>>9429218
There's no scientific consensus on what "spin" actually is so there's no way to know for sure how it affects magnetism.

"Spin" isnt a literal spin btw. Its not like spinning a dreidel. Its just a word used to describe how an electron moves in a magnetic field. A particular "spin" has a particular motion.

>>9429310
If thats what you want to do, then yes. The US has aerospace bachelors. But Im sure a program will take mech eng.

>>9430471
Get a visa from where?

>>9430884
Research assistant? Codemonkey?

I can think of lots of other indirect ways. But it depends on your interests and abilities.

>>9430837
>what do they mean in higher level math when they say 'is an isomorphism'
If you have sets with some structure (groups, vector spaces, topological spaces) you usually define a notion of maps between the sets which in some sense preserves that structure. Such a mapping is an isomorphism if it has an inverse.
So two such sets [math]A[/math] and [math]B[/math] are isomorphic if there exists an isomorphism [math]f : A \to B[/math].
>something to do with bijection?
The existence of an isomorphism implies there is a bijection, the other way around doesn't always hold, for example with topological spaces.

particles aligned by charge = magnet
right?

>>9430837
An isomorphism is a morphism with a 2-sided inverse (w.r.t composition).

The definition of morphism depends on what category you work in.

>>9422464
Will it become theoretically possible that we could make women grow to be much taller, more voluptious, and sexually aggressive, and males much shorter, skinnier, and more feminized?

>>9422464
Is it okay if I don't actually understand the "why" part of solving problems early in my math career? I mean things like "completing the square" I know how to calculate it and all but I don't have any real understanding of the underlying principles. I've taken a look at proofs books and most of them assume a certain level of math knowledge that I don't have, for example they assume you've already taken a high school level course on calculus/trig/etc. Is it reasonable for me to just go on foIlowing the traditional route of algebra -> geometry -> trig -> "precalc" -> calc -> Actual Math?

>>9422464
Is math related to science?

since a body remains at rest or continues at same velocity unless a force acts upon it, why do we not constantly fall when we go down in an elevator?

>>9431634
>why do we not constantly fall when we go down in an elevator?
you do, that's how you go down, and there is a net downward force acting on your body as you begin to descend

Is it gay to kiss my bofriend after he sucks my dick?

>>9431653
thanks anon, that makes sense

>>9430837
It is typically only sensible to look at mathematical structures up to isomorphism.
Consider for example [math]\mathbb R[/math] and [math]\mathbb F:=\{(r,0):r\in\mathbb R\}\subset\mathbb C[/math]. Clearly [math]\mathbb R\not\subset\mathbb C[/math]. However, it is easy to show that [math]\mathbb R[/math] and [math]\mathbb F[/math] are isomorphic, so we may safely take [math]\mathbb F[/math] to be another representation of [math]\mathbb R[/math]. In fact, the reals are often defined to be the unique, up to isomorphism, order-complete field. In this manner, it is perfectly valid to call [math]\mathbb F[/math] the reals and say that the reals are contained in [math]\mathbb C[/math].

Are radians vs degrees similar to metric units vs imperial units

>>9431999
not really, one just measures things in a straight line and the other measures curves or something

>>9431999
More like Kelvin vs Fahrenheit

Hey, trying to getinto wastewater treatment. Can anyone reccommend any good bio treatment books?

I'm sorta confused. What sort of sorcery can make the derivative of this sqrt flip like that? how did they manipulate to get 2/3 instead of 3/2?

>>9432246
>how did they manipulate to get 2/3 instead of 3/2?
Look at which side the du is on.

>>9432291
god dammit. these are the reasons I fuck up on tests

How do I factor an equation in the form of :
[math]x^2 + y^2 + z^2 + xy + xz +yz[/math]
Don't know what it's called so I don't know what to look for.

>>9432549
>How do I factor an equation in the form of :
>x2+y2+z2+xy+xz+yz
Why do you think you can?

>>9432572
Obviously not that exact function, but more like this.
I'm supposed to find perfect squares and I'm just lost.

>>9426784
I thought I was too old and I'm 20
The only thing stopping you is yourself.

>>9432588
I don't think there is any general method. It's doable if you know that the roots form a sphere or some other nice shape.

What type/s of geological surface/s are seen in the image
fault trace, normal fault and shear zone? can anyone see anything else?

>>9432859
Rocks.

>>9432588
what's the goal here?
are you trying to find "a" solution, all solutions until a certain threshold, or a method of finding all of them pythagorean triple style?
If it's one of the first two, I suggest to just brute force it with a computer. If it's the third I wish you the best of luck.
Here are all solutions for x,y,z being natural numbers between 1 and 10

>>9432549
It's called a quadric. Such equations can be written in matrix form as x^T.A.x where A is a symmetric matrix (you need to use homogeneous coordinates if the equation has a constant term). In turn, a symmetric matrix A can be decomposed to A=S^T.B.S where B is diagonal and S is orthogonal. Thus the equation can be written as x^T.S^T.B.S.x = (S.x)^T.B.(S.x). In essence, S performs a change of axis so that the equation is a sum of squares.

Why is LSD even illegal?

>>9422464
what happens to your master or phd thesis in case your supervisor dies out of a sudden?

>>9433540
Jesus christ anon not here you need to keep that shit low key

>>9433540
>what happens to your master or phd thesis in case your supervisor dies out of a sudden?
You need to find a new supervisor

I knew someone whose supervisor got brain cancer so he had to get a new one

>>9433577
>You need to find a new supervisor
isn't it the duty of the university to assign a new one to you?

>>9425339
>>9425339
>you can't multiply any matrix by a 1x1 matrix

Sure you can:

A [a] = aA

say you want to calculate Φ of a complex number z=a+b*i then you would use the formula Φ= arctan (b/a) the answer the answer would be a decimal number ( lets say 1.10) are they radiants or what? how do i pass them as degrees of a circumference expressed as pi/6 and the such?

>>9434263
on the same line, how would you go about calculating Z1+Z2 and then expressing it in form r*e^(i*Φ)

>>9434263
In most languages, trig functions use radians. Multiply by 180/pi to convert to degrees. But for rectangular->polar conversion, check whether you have a 2-argument form of atan() (e.g. atan2() in C), as that will get the quadrant correct.

>>9422464
Any tips on how to do this? My understanding is that I'll need to solve the Schrodinger equation and determine the exact wavefunctions. Is there another trick I'm missing?

>>9434412
Forgot image