/sci/ - Science & Math

>>9596221
Explain elementary proportions to me.

>>9596221
Can someone explain to me what the real issue is holding up the proof of the reimplantar hypothesis? Or some good intro papers or texts? I’d like to understand it

I recently heard about it and kinda became interested in it because of how simple the original euler zeta function was. But I also found out it’s a meme... so it’s hard to get good resources from people.

>>9596235
*Reimman

Sorry

>>9596221
Do you have to be a far-right douchebag in order to love science?

>>9596277
want fuck laura southern.. must donate to patreon accunt..

>>9596321
Yeah dude, I'm gonna go empty my paycheck in there so maybe she'll look at me

Is it normal to hate Analysis?

>>9596237
Riemann*

>>9596795
no real men love anal

>>9596221
This is a problem on my complex analysis class. Given a Riemann Surface W_0 and a compact subset K_0 such that the Riemann Surface W = W_0 \ K_0 there's a point in W say p_0 such that a local barrier exists. Show that Green's function exists.

I tried looking at the solution over the complex plane, Ahlfors creates these two functions that bound the supremum of harmonic functions (Lemma's 1 and 2 around page 240-250 3rd edition) but the problem is the corresponding class of harmonic functions over Riemann surfaces has this log(z(p)) part where z is a coordinate map so it's very difficult to bound. I think you'd have to use the fact K_0 is compact but I'm not sure how. Any anons have some tips?

Pic related #3

Didn't get an answer for this on the last thread, how do I apply algebraic structure (that of abstract algebra) to the surfaces of manifolds? Do I use atlases or something else entirely?

Are chromatin remodeling complexes the same as histone tail modification?

>>9596221
give the _rigorous_ definition of spin, please

how much overlap is there between aerospace engineering and astrophysics?

please respond. please don't bully me.

>>9596795
Yes.
>>9597039
Building planes and studying stars.
Only when you build planes that travel to space do they overlap.

>>9597062
>Only when you build planes that travel to space do they overlap.

what kind of overlap exists there? again, please no bullying.

>>9596221
How do I prove a group is closed under operation?

>>9597113
>How do I prove a group is closed under operation?
Show that the composition of two elements under the operation is still an element of the group.

Any tips to memorize British and American unit system?
Inches, pounds, feet, Fahrenheit, pounds force, psi...
Come on

Also, what is the difference between lbf/in^2 and lbf/ft^2 ?

God, this is a mess

Where can I read upon how electricity works?
Im trying to understand the basics so later I can understand how x-rays are created.

I am not native English speaker.
Youtube videos with Wikipedia definitions or flat out half assed explanations go over my head.
I need the basics explained like what is Volt,Amp ect. in a mater that is concise and understandable,and there is a concrete industry standardized in the terms used in the explanation since again I am not native English person and a lot of analogue terms make me even more confused.

>>9596221
Really stupid one.

Let's say we have a RLC circuit.
There is XL XC and R.
How would you word the difference between XL and R ? In some cases when I read "the resistance of coild is...." it's actually R not XL
So how do I differentiate between those two in text?
Also how is it with capacitor? How is the wording there?

>>9597113
The group is a set with multiplication
weither an element is in the set depends on some property.
you show that this property holds for the product of two elements from the set.

>>9597113
If you know its a group then its closed under the group operation by definition.

If there is very little matter in the space, wouldnt the fact of "0 kelvin temperature" be irrelevant? In other words, wouldnt a body thrown into open space keep its internal temperature almost indefinitely, with no or very little particles to transfer heat to?

>>9597762
same anon as >>9597762
I study electrical engineering so I should be able to do this.

I'll keep it simple like they did in my school because I am not quantum physicist.

Current is ordered flow of electrons and it's unit is A or "Amp"
I'll use our favourite water analogy DC is just like water flow but with electrons.
AC is electron going back and forth the higher the frequency the faster they go back and forth.

voltage unit V or "volt"
To this day I can't imagine it so I'll give you an analogy. imagine spring between each electron the more compressed the spring is the higher repel force between the electrons.
I gave up on imagining voltage I look at it this way
You can't have current without voltage so in your wall socket there is voltage between the two holes. Let's say it's "energy" between those two points, the higher the energy the further the electrons can go.
Also the definition of voltage itself is difference between two points. You can't have voltage in one point you always measure two.
So let's say it's "pressure" between those two electrons. The higher it is the more they repel the further they go.
I am not going to start with speed that's a rabbit hole.

Resistance unit Ω or "ohm"
The definition they told me is "the flow of particles with opposite charges in opposite direction as current" Think about resistance as the measure of the difficulty to pass for current.
Everything has resistance even the cable itself.
Without resistance you can have current in closed circuit theoretically forever. This is done with extreme cold it's used in CT machines.
The heat electricity produces is resistance as well.

So which way does current flows? Another good question. The answer is both directions.
Because flow of positive charges is electricity as well. But we say from + to - because that's the flow of positive chargers - is the flow of electrons.
Another important thing:
Current wont flow if your circuit isn't closed. That's how switch works.

>>9597809
Alright that is more understandable than 90% of the shit ive read so far.
Thank man.

>>9597823
my keyboard is failing so pardon my grammatical errors.

>>9597800
Only if that body can withstand the vacuum pressure

>>9597826
Okay, so temperature is not a concern but the pressure is, since said body will "want" to reach the same level of pressure around it(?). Thanks!

Retard here, trying to comprehend vectors
I'm supposed to calculate the distance between Q and the plain and realize that it's 0, meaing Q is on the plain

Besides what's on the drawing the task gives me the normal unit vector for the plain, called n
If I go Q - P0 to get the distance (I'll call it s, it's a vector) and scarlarly multiplay s with n the result is 0, so s and n are orthogonal

Is that proof of the distance between Q and the plain being 0?

There's an earlier example in my book where they calculate the shortest distance between the point and a line, the book says to look at that for help
In that task they calculate the distance s between the points Q and P0 like I did, but then they project it down onto the line, calculate another vector d from the tip of that projection back to Q, and the magnitude of that vector d is the shortest distance. Makes sense.
The difference here being that the point is away from the line and it's a line instead of a plain

Now if I try and project s down in my plain task the result is 0 because of orthogonal memery, meaning d is s, s has a magnitude meaning there would be a distance
I'm just supposed to get to where shit is orthogonal and quit, right?

I'm a total brainlet, with math I need someone to show me the exact task with different numbers so I can go "ah yes I understand what is being done here and why", I have massive trouble making any sort of connections on my own
Sorry for the drawing I'm on my mom's laptop and there's no mouse

>>9598046
Is there a better drawing?

>>9598055
No, that's what I have to work with. I didn't leave anything out
Only thing I maybe should have made clear is that P0, e1 and e2 is what makes the plain, the plain E is P0 + variable1 * e1 + variable2 * e2
They give me all those vectors, but P0 seems to be the only useful one outside of maybe calculating a normal vector for the plain but they gave me that

>>9597749
forget it exists and use metric

why are low test soy asians so good at science? is soy the secret to science?

>>9598046
>Is that proof of the distance between Q and the plain being 0?
Yes
>Now if I try and project s down in my plain task the result is 0 because of orthogonal memery
s is parallel to the plane, so the component of s along the normal vector to the plane is 0.
>s has a magnitude meaning there would be a distance
A non-zero distance between Q and P0, not between Q and the plane.

>>9598079
>s is parallel to the plane, so the component of s along the normal vector to the plane is 0.
Very helpful, I sort of couldn't put that together but now that you said it it really makes a lot of sense
Thanks Anon!

what is it called when you "cut up" regions in complex analysis?
for example when proving the residue theorem you can cut up the region as in the two pictures and prove it both ways.
i've heard the word surgery used, but im not sure if that's right

How the fuck do you learn chemistry?
Math and physics are easy because advanced concepts are built on easy to understand concepts, but chemistry is the opposite because you have to accept that "it just werks".

>>9598331
There's no standard term for this. You would just describe choosing two different paths of integration

>>9597800
It would cool by radiation only. For a warm-blooded creature (e.g. human), that's nowhere near enough to get rid of body heat, so without some form of active cooling you'd die from overheating.

The temperature of space refers to the equilibrium temperature for an inanimate object which isn't generating heat internally. I.e. the temperature at which absorbed radiation equals emitted radiation.

Why?
I've got
[eqn] \lim\limits_{x\to x_0}\dfrac{f(x)-f(x_0)}{x-x_0}=f'(x_0)\,; \\
\lim\limits_{x\to x_0}\dfrac{f(x)-f(x_0)-f'(x_0)(x-x_0)}{x-x_0}=0 [/eqn]
but i can't see where to go from there, and i feel like i'm missing the o() part.

hoe does xlogx = xln(x)

>>9599156
>Why?
What do you mean? It is a definition.

>>9599182
>It is a definition.
i didnt know that. i guess i meant why are the two definitions equivalent then

>>9597749
Lbf/in^2 is the pressure exerted by 1 Lbf over a one inch by one inch area.
Lbf/ft^2 is the pressure exerted by 1 Lbf over a one foot by one foot area.
1 Lbf/in^2 is 144 greater than 1 Lbf/ft^2.

To memorize British and American units, just do some practice problems, make a conversion sheet. Comes with doing it a lot.

>>9598336
General chemistry or what?

>>9596221
In this universe, it seems that things do not occur in isolation. Bacteria, religiotards, dog shit, planets, galaxies. Find one of anything and you will likely find millions.
It is reasonable to infer from this that the big bang is likely to be one of many. If so, we would be surrounded in all directions by other universes. The gravity of this huge surrounding mass would explain the accelerating rate of expansion of our universe.
No?

>>9599241
not necessarily
https://en.wikipedia.org/wiki/Shell_theorem

While it might be true, it would mean a non-uniform acceleration meaning we could see different expansion rates in different directions. We couldn't see uniform acceleration in your scenario because of the shell theorem.

I'm currently reading through several tough textbooks.

Would my time be best spent narrowing it down to one, and focusing strictly on that? Currently I bounce daily between, primarily, Spivak's Calculus, Knuth's Cocnrete Mathematics and Hoffman and Kunze's Linear Algebra. When I get BTFO and depressed by any or all, I often peruse easier works like Book of Proof / How to Prove It, or supplementary stuff like Tao's or Landau's work in analysis, MIT's Math for CS lecture notes, etc.

Is my strat shit or bretty gud? Anecdotally, I've noticed leaving and coming back with a fresh perspective is incredibly helpful. But perhaps it's more efficient to focus on one work at a time with monk like focus?


Pic absolutely not related

>>9599328
might be worth noting I don't strictly adhere to opening each one each day, I take it as it comes. Sometimes I'll be on one all week, other times I'll cycle each frequently in one day.

>>9599156
The o() means there's a function that goes to zero faster than [math]x-x_0[/math]. Basically [math]\lim_{x\to x_0}\frac{f(x)}{x-x_0}=0\Leftrightarrow f(x)\in o(x-x_0)[/math]. Let [math]g(x)=f(x)-f(x_0)-f'(x_0)(x-x_0)[/math], and the previous statement gives you [math]g(x)\in o(x-x_0)[/math]. Denote [math]y=f(x),y_0=f(x_0)[/math] to get [math]y-y_0=f'(x_0)(x-x_0)+g(x)[/math]. The [math]g[/math] is usually just denoted [math]o(x-x_0)[/math], since it's an insignificant function anyways. Same thing works backwards, so the definitions are equivalent.

I'm really stuck on Thevenin Equivalent circuits.

I know how to get the equivalent resistance; I simply short circuit voltage sources and "open" the circuit where I want to put the two terminals of my resulting circuit

What Im' really stuck on is doing the Thevenin-Equivalent voltage.

Here's my thought process for solving the circuit in pic related.
They ask me to use Thevenin to get the current going through the ten-ohm resistor.
To get the thevenin-equivalent voltage, I short-circuit the 6-volt source and have an open circuit at the ten-ohms.
Now, we have a 5,20 ohm resistors in parallel, giving us four ohms. We then have 4-5-15 resistors in series, so this gives us
[math] R_{th} = 24 \Omega [/math]

Solving for the thevenin voltage, we open the circuit at the ten-ohm resistor and keep the 6V Source.
We have four volts going through the 20 Ohm and the 5-15Ohm branches, which means we have three ohms going through the 15-ohm resistor.
The 15-ohm and 10-ohm resistors are in parallel, so [math] V_{TH} = 3V [/math]

Finding the current through the ten-ohm resistor is thus
[math]
I = \frac{V_{TH}}{R_TH + 10} = \frac{3 } {34} = 0.088 A
[/math]

But when I look at the answer, I get that the result is 0.192 A. Where am I going wrong? I'm assuming it's the thevenin voltage expressions, but I'm not sure.

>>9599392
>we have a 5,20 ohm resistors in parallel, giving us four ohms
this is correct

>We then have 4-5-15 resistors in series
this is wrong look at it again

the thevenin voltage was calculated correctly, but don't ever say that you have voltage through, say voltage across

>>9599377
Thanks!
I just saw another proof in a video that went like
[math]\cdots\Longleftrightarrow g(x)(x-x_0)=f(x)-f(x_0)-f'(x_0)(x-x_0)\text{ and } \lim\limits_{x\to x_0}g(x)=0\\ \Longleftrightarrow f(x)-f(x_0)=f'(x_0)(x-x_0)+g(x)(x-x_0)\text{ and } \lim\limits_{x\to x_0}g(x)=0\\ \Longleftrightarrow y-y_0=f'(x_0)(x-x_0)+\mathcal{o}(x-x_0)[/math]
Though I guess they're both the same since, in a hand-wavy sort of way, if g(x) goes to zero faster than x-x0, then g(x)(x-x0) will too.

does anyone have a copy of rudins memoirs? "the way i see it"

>>9599479
>does anyone have a copy of rudins memoirs?
Rudin is a meme.

when finding the curvature of a vector function. I understand it to be (dT/ds)/(ds/dt). Since ds/dt represents the change of length over a instant in time, why is it that ds/dt isnt a constant value since at any given instant moment in time the length is always the same?
idk if im making sense hopefully u guys get my question

>>9599831
also, whats the reasoning for having unit tangent vectors instead of just tangent vectors

lads how do I show symmetry and transitivity of this relation

>>9600000
What have you tried?

>>9599479
https://www.amazon.com/Way-Remember-History-Mathematics-V/dp/0821806335

>>9599840
a_r = v^2 / r_curvature

>>9599328
Jesus anon why do you need so much MATH

>>9596221
Can I get a quick rundown on [math]\mathb{Z}_n[\math] and its properties under "addition"?

>>9600318
[math]\mathbb{Z}_n[/math]

>>9600318
>>9600321
Aye baby
https://en.wikipedia.org/wiki/Integer

>>9600330
Nothing there about the sets of integers mod n

>>9600330
Look I'll just post the question and hope that someone spoonfeeds me.
A line is defined as the equation ax + by + c = 0.
I already have the solution but not the procedure to getting to the solution, so if someone could explain it (perhaps step-by-step) I'd be eternally grateful

>>9600340
You asked about the localization of [math]\mathbb{Z}[/math] at an integer [math]n[/math], not about "sets of integers mod n".
>>9600352
There seems to be a typo as [math]\mathbb{Z}_7[/math] is not a field.

>>9600352
First point gives [math]a0+b0+c=0\to c=0[/math]. Show [math]b\neq 0[/math] using the second point and get [math]kx+y=0[/math], where [math]k=b^{-1}a[/math]; note that a solution [math](a,b)[/math] is not unique since you can always multiply the equation. Plug in second point to get [math]k=-6[/math].
>>9600373
I'm pretty sure 7 is prime.

>>9600375
>I'm pretty sure 7 is prime.
Yes, and?

If I know g, how do I find f in [math]\nabla\times f = g[/math]. I’m talking about very simple cases like g=(2x,0,-2z). My lecturer seemed to find f easily, but I can’t think how to do it without looking at a load of PDEs
>>9600000
Symmetry’s easy. If a/b=2^k, with k in Z and a, b in N, then b/a=1/(a/b)=2^{-k}=2^k’, with k’ in Z and k’=-k. Hence, b~a. Transitivity isn’t much harder, basically start with a/c and show it’s of the form 2^k.

>>9600380
Integers mod [math]q[/math], where [math]q[/math] is a prime power, are finite fields.

>>9600383
Sorry, I worded that wrong. Integers mod [math]p[/math] for prime [math]p[/math] are finite fields and you can build fields for prime powers.

Any anons mind helping me with this transformation efficiency problem? I'm a bit of a brainlet and I'm stumped. All the examples I've seen/had were much simpler.

>>9600385
Yes, and? That still doesn't make [math]\mathbb{Z}_7[/math] a field since the ideal consisting of all elements of the form [math]\frac{3n}{7^k}[/math] in it is neither 0 nor the whole ring.

What does the dz/dx mean here?

it makes sense to write df/dx, in which you differentiate the function f, with respect to x, but in the pic related example the solution doesn't make any sense to me, where does the z^2 in the next line come from?

Could someone please do the computation between the two first lines as detailed as possible, so i see what's being done.

>>9600393
I don't see what you mean. The field [math]\mathbb Z_7=\mathbb Z/\langle 7\rangle[/math] is generated by the ideal [math]\langle 7\rangle[/math], which is maximal and therefore the quotient ring is a field.

>>9600398
>[math]\mathbb Z_7=\mathbb Z/\langle 7\rangle[/math]
This is false since every ideal in a field is either 0 or the entire field, which is not the case with the ideal in my previous post.

Aight lads, figured out my problem.

Anyone familiar with calculating transformation efficiencies of colonies? Just need a check before I submit it ;x

>>9600407
[math]\mathbb Z[/math] is a ring, not a field. If you want to consider ideals over [math]\mathbb Z_7[/math], just note that it has a multiplicative group [math]\mathbb Z_7\setminus\{0\}[/math] and it follows that the ideal is either 0 or [math]\mathbb Z_7[/math].

>>9600396
you differentiate z with respect to x, but 2(x^2 + y^2) pops up in the denominator which is just z^2.
this whole solution is an extreme abuse of notation and you just need to deal with it until you take your differential geometry class or whatever.

Do I understand it right that if we define S as bunch of S1,S2,S3,Sn where T= dt*n then Sn will be V (velocity)?

Talking about linear constant speed motion

>>9600420
[math]\mathbb{Z}_7[/math] is not a field since [math]\frac{3}{7}[/math] in [math]\mathbb{Z}_7[/math] is both non-zero and not a unit.
Assume it is zero, then [math]7^k \cdot 3 = 0[/math] in [math]\mathbb{Z}[/math] for some [math]k \in \mathbb{N}[/math]. Assume it is a unit, then the set consisting of elements of the form [math]\frac{3n}{7^k}[/math] is a prime ideal which contains a unit.

>>9600418
This isn't my field at all, but how come the efficiency is way over the 0-100 range?

>>9600536
There is no [math]7^{-1}[/math] in [math]\mathbb Z_7[/math] and neither is there 3/7. It's not required by field axioms either, since [math]7=0[/math].

I'm currently a first-year Electrical Engineering major. I want to get possibly get into AI and robotics and also possibly neuron-controlled prosthetic limbs.

What should I learn for each of the two if I want to be really good at that field?

>>9600565
I'd start with Iron man 1 and then work progressively through the series from there. Take note of what the main character does when he encounters a problem.

>>9600576
What's the best way to get captured by terrorists who want me to build missiles for them?

>>9600564
>There is no 7−1 in Z7
7 is trivially a power of 7 and is thus a unit in [math]\mathbb{Z}_7[/math].
>neither is there 3/7
What are you talking about? Is 3 not an integer?
> since 7=0.
Units cannot be nilpotent in a non-trivial ring.

given linear equation

x + y = 15

How do I properly write the range of all [math]\mathbb{N}[/math] numbers for x/y pairs which satisfy the equation?
It will be something like n-x + x i.e. 15-3 + 3

>>9600630
Find me an integer [math]n[/math] such that [math]7n=1 \mod 7[/math]. Clearly it doesn't exist, so 7 has no inverse.

>>9600565
seriously though. What should I learn? I'm kinda proficient in c++ and cad software but what should I know? What's the best way to learn about neural networks?

>>9600637
Yes, 7 is a nilpotent in [math]\mathbb{Z}/(7)[/math] and is thus not a unit. Your point?

>>9600375
>>9600352
Having trouble with the follow up too. (Sorry, supreme-brainlet here)
A line [math]r[/math],
[math]a_1x_1+b_1y_2+c_1=0[/math] is parallel to line [math]s[/math] : [math]a_2x_2+b_2x_2+c_2=0[/math] if no pair [math](x,y)[/math] satisfy both equations when plugged in.

I know there's such a line because from the axioms of affine space, for any two points P and Q there must be a line that passes through both.

Plugging in (0,1) and (1,0) into the general equation for a line implies that a_1 = b_1 = c_1, so my thinking is if I simply go through {1,2,3,4,5,6}

for (0,1) and a = 1, 1*0 + 1*1 + 1 = 2 != 0
for a = 2, 2*0+2*1+2=4 != 0
for a = 3, 3*0+3*1+3=6 != 0
for a = 4, 4*0+4*1+4=8=1 != 0
and so on, so no choice seems to make sense?

I wrote the stuff above for those who get angry at people who ask questions without putting any effort in, it's fine if you don't read it and just spoonfeed the answer. Thank in advance

>>9596221
a-b=11
a+b=90
a,b=?

>>9600712
1) what is the equation of the line they are asking about, it would help to find that wouldn't it?
2) parallel lines have the same slope

is libgen illegal?
i wanna get about 100 files but will it set off alarms at my isp?

>>9600877
b = - 11 + a
a+b = 90
a + (-11+a) = 90
2a = 90+11
2a = 101
a = 101/2

simple linear equation y = kx+m

>>9600950
no

>>9600000
check'd!

>>9600563

It's just how it is ;x

Weird I know...

Is it true that the universe has no value at all, and that we're just a complicated form of nothing? Because is there an equal amount of matter and antimatter?

There is a two variable, associative, commutative operation [math]*[/math] on the set [math]S[/math], with the property [math]\forall x,y\in S, \exists z\in S: x*z=y[/math].
Does this imply that S is closed under the above operation?

>>9600000
for every k there is some negative k
???

>>9600950
>is free knowledge legal
lol

where do i purchase hard copies of old textbooks (like secondhand)? The used bookstores around here don't have any

>>9600000
have you tried checking them?

>tfw graduating after finals next week and have a job
>tfw not even studying for finals

If hbar relates the frequency of light to the energy of a single photon, is there a similar constant which relates the frequency of gravitational waves to the energy of a single graviton? If so, does it have a name, and can we know its value?

If you were to compress five years into twenty four hours what would be the scale of time?

I have a tensor of type (0,2) which is symetric, i.e. [math]T_{ij}=T_{ji}[/math] in some basis. Iím supposed to show that it must be symetric under any change of basis, but I'm not sure about how using the transformation law that is in my by book, in a new basis [math]T_{i'j'} =T_{ij}A^{i}_{i'} A^{j}_{j'}=T_{ji}\left(A^{i'}_{i}A^{j'}_{'}\right)^t [/math] But I don't know how to make it in a way to get to [math]T_{j'i'}[/math]

Anyone familiar with probability here?

In Jaynes "Probability Theory The Logic of Science" on page 66 he tries to explain eq 3.59. But it does not make sense to me:

> The Information R_later [...] reduces the number of balls in the urn available for the first draw by two, because it assures the robot that there are two later draws in which two balls are removed.

But this makes no sense, since the robot also knows this for the right part of the inequality 3.59, since the robot knows B, and B includes that there will be 3 draws in total, so two later draws.

Can anyone explain this? You can find the book here: http://www.med.mcgill.ca/epidemiology/hanley/bios601/GaussianModel/JaynesProbabilityTheory.pdf

How do you find the indefinite integral of the inverse of a function?

>>9601692
>How do you find the indefinite integral of the inverse of a function?
https://en.wikipedia.org/wiki/Integral_of_inverse_functions

>>9601645
I'm not downloading a book to compensate for your laziness.

Any tips on how to solve this meme?
I know it's possible because my calculator can do it

And I'm pretty sure I need to use cos(x)^2+sin(x)^2=1 type of stuff
But I have absolutely no idea where to start, I've tried squaring one or both equations and adding or subtracting them, but all I got is pages full of nonsense

>>9601692
>>9601707
Whoops, I meant the reciprocal of a function.

>>9601722
Why do you suppose this should always be possible?

>>9601716
oh I think my calculator is cheating by replacing sin(30) and cos(30) with b/2 and (sqrt(3)*b)/2
I'll try fucking around with that and report back, I think this might make it easier to subtract one equation from the other

>>9601708
Here.

>>9601725
Maybe it is not always possible, but is there a method to work it out for the set of functions it is possible for?

>>9601728
>>9601716
I did it!
With the aid of my trusty calculator, at one point I just had to type in what cos(20)*sqrt(3)-sin(20) was and divide some ridiculous numbers
Still wish I could do it without, but I'm not so sure that's possible anymore

>>9601716
[eqn]\pmatrix{\cos(20) & \sin(30) \\ \sin(20) & \cos(30)} \times \pmatrix{a \\ b} = \pmatrix{4 \\ 3}[/eqn]

So you need to find the inverse of [math]A = \pmatrix{\cos(20) & \sin(30) \\ \sin(20) & \cos(30)}[/math].

[math]A^{-1} = \pmatrix{a & b \\ c & d}^{-1} = \frac{1}{\det(A)}\pmatrix{d & -b \\ -c & a}[/math] where [math]\det(A) = ad-bc[/math].

>>9601210
Intredasting.

>>9601838
Thank you!
I'll go through the thing again tomorrow and try it that way

>>9601969
note that I confusingly used the variables "a" and "b" in two different ways, sorry about that

>>9601994
It's ok, I could tell what you meant

>>9601243
i think yes. it must have an identity element and the existence of inverses. from that you can rewrite the last property as "for all x,y in S there exists a z in S such that z=x*y"

>>9600565
anyone gonna answer this?

What's the problem with the set of all sets containing itself?

>>9600121
just a neet having a good time

Why can't they just say "y is a solution if it's (...) and replacing y any y' in the ODE makes it an identity"?

>>9596221
/sci/ I fucked up...

I was reading a few books and was too lazy to get out of bed. I tried to put it back on the shelf and it collapsed. Long story short I am under a pile of books now and my rib cage feels obliterated. Should I go to the doctor?

>>9596221
Can anyone help me out here? For pic related I got A, but it says the answer is D.

Sec^2x == tan^2x+1, so I have tan^2x = 3, so I solve for tan x = +/- sqrt(3). Tangent is equal to sqrt(3) at pi/3,2pi/3,4pi/3, and 5pi/3.

Up to that point my answer agrees with the listed one, but I thought the period of tan was pi, right? So shouldn't it be place pi k, and not 2pi k?

>>9602512
forgot picture related for the problem.
>>9602477
post pics

>>9602512
[math]\tan^2(x)[/math] doesn't have a period of pi though

>>9602477
Leave it to /sci/ to die in the most autistic way possible.

>>9602518
(sec(x) + 2)(sec(x) - 2) = 0

That's the easiest way to solve it. Also unless I'm being really dumb C and D are equivalent.

>>9602540
>>9602543
okay, ty frends

>>9602518
>>9602543
I didn't actually read your post, just looked at the picture. As far as I can tell A, C, and D are equivalent and whoever made the problem is dumb.

>>9602477

"Science... Why have you foresaken me?"

Please actualy die because of this. The bants would be perpetual. Literally you would become an art piece and a living (or rather dead) metaphore for the exhaustion of the persuit of knowledge.

>tfw your studies literally killed you.
>yfw crushed under the weight of your own knowledge.

Kek.

>>9596221
intuiton for l hospital rule for infinity/infinity?

brainlet here trying to learn, can someone show me how to do this question? i know i need to find an equation and find the minimum

>>9602792
S = v/t
t = s/v
12km / 30km/h = 0.4h

Boat expenses = 3.00 * 0.4

Bus expenses = 20 * 0.06

Total = bus expenses + boat expenses

If we assume that the destination point is on shore as well and lake is long enough to the south then we can use Pythagoras theorem about the length of hypotenuse in a straight-angle triangle:

c^2 = a^2+b^2
c = sqrt(12^+20^) ~ 23.3Km

Then we can theoretically travel by boat with 23.3*3

>>9602811
I actually did this, but this question is in a calculus assignment, so i assumed that it was more complex and I was missing something. But maybe I'm overthinking it, idk

>>9602823
What the last topic you've studied then? Should be relevant in context? Werent there any in-class/in-auditorium example questions?

>>9602792
Assuming he drives the boat in a straight line, draw a plot of the paths he takes in the boat and bus. Use a variable for the boat distance, then write the bus distance as a function of the boat distance. Write the total cost as a function of these two distances, which is then a function of just boat distance.

Now that you have total cost as a function of boat distance, take the derivative and set it equal to 0 to find the minimum.

>>9602195
Thanks, I got to the same conclusion, I actually only needed the existence of identity/inverse to solve my problem, and just had to reformulate my proof of those to avoid closed-ness, but from those it follows.

I have an internship phone interview today and Im scared shitless, how should I prepare? Only other interview Ive done was for a university in person (interview was good, my gpa and sat were not). Last two jobs had no interview (manual labor type jobs). Other people that got interviewed said it was mostly behavioral things, should I just act natural and go with the flow?

I'm going through a past paper for a maths exam aimed at 16 year olds, and this question appears to require the candidate to produce a reasonably accurate value for cos(50deg) or sin(40deg), neither of which are on the unit circle or otherwise commonly learned as far as I know, without a calculator.

Please explain to a brainlet how the student is expected to go about this.

>>9603382
Of course you do long division to change 50' into arc length, ie. 50'=2pi*50'/360'=pi/3,6~0,873
Then you take this value and put into the Taylor series for cos which is [math]\sum_n=0^\infty(-1)^n\frac{x^{2n}}{(2n)!}[/math] and take enough terms that the first digit stops changing... or you could tell your young relative to read the test or tell the school to get its shit together.

So I'm having some trouble understanding line integrals. When I try and solve a problem like [math]\oint_{\partial R}^{ } {y}^{2} dx + {x}^{2}y dy , R = \left \{ \left ( x,y \right ) \mid 0 \leq x \leq 5 , 0 \leq y \leq 4 \right \}[/math] using Green's Theorem, I get 120. But when I try and solve it by computing the line integrals of the 4 edges of the rectangle, I get 0 for each of them, and I don't understand what I'm doing wrong.

Like If I try to compute the line integral of the bottom edge, the parametric equation of the path would be [math]\mathbf{r}(t) = \left \langle 5t, 0\right \rangle, 0 \leq t \leq 1[/math], and its tangent vector would be [math]{\mathbf{r}}'(t) = \left \langle 5, 0\right \rangle[/math].

And so the line integral would be [math]\int_{0}^{1} \left \langle {\left ( 0 \right )}^{2}, {5t}^{2}\left ( 0 \right ) \right \rangle \cdot \left \langle 5, 0 \right \rangle dt = \int_{0}^{1} \left \langle 0, 0 \right \rangle \cdot \left \langle 5, 0 \right \rangle dt = \int_{0}^{1}0 dt = 0[/math].

>>9603437
The integral along the y=0 is obviously going to be 0. But the others shouldn't, so try including one of those as an example.

I know this should be going on /adv/ but that place is more helpful for relationship stuff

So I’m a molecular biology major who has been doing a minor in computer science. Well, it turns out that I’m starting to like my computer science classes much more than my biology major classes, even the higher-level stuff. If I switch majors, I would still be able to graduate on time.

Should I make the switch? I would like to go to graduate school and eventually work in data science or something similar, but I’m not sure about the job prospects. Is it a good idea to have a CS degree in Southern California, or would I be better off job-wise with a molecular biology one?

>>9603423
>50'=2pi*50'/360'=pi/3,6~0,873
not him but how did you get
>pi/3,6~0,873
2pi*50'/360 | /2
pi*25/180 = pi*0,139

>>9603636
When you divide by 2 you either remove the 2 or divide 50 by 2, not both, because you've just divided by 4.

>>9603657
right, my bad, read it as + for some reason
well it is still will be
pi*50/180 = pi*0,27777777777777777777

Is this correct?

>>9603667
that's... the exact same thing

Lads, what do I do next? I am a turbo brainlet?

>>9603767
make a fucking proper photo

What is Calculus 1, 2, and 3?
First year I read "One variable calculus" (=Calc1?),
"Linear Algebra" (=Calc2?), and
"Multiple variable calculus" (=Calc3?)
>t. not american

>>9603683
Bump

>>9603811
Calc 1: limits, differentiation, optimization, basic integration
Calc 2: integration techniques, sequences, series, Taylor series, basic DEs, polar coordinates

>>9603683
Yes, but put the answer in Hz.
Or THz (terahertz) if you want

>>9603811
Calc 3 is multivariable
Calc 4 is diff eqs

Retard question.
Like really retarded.

Why in

3+ 8 * (6-2) + 11 = 46

And not 55?

I thought you just do (6-2) which is 4
And then go back to the beginning

So 3+8 is 11 times 4 which is 44 + 11 =55

Why do we multiply 4 with 8 first?

>>9603913
No
The order of execution
let's simplify:

3+8*4+11 = 46

The hard rules are: division and multiplication ALWAYS takes priority over addition and subtraction (exception - special cases and notations like parenthesis, etc).

Knowing that, we understand that first action is the multiplication, therefore:

3+(8*4)+11 = 46
3+32+11 = 46

>>9603923
>the hard rules are: division and multiplication ALWAYS takes priority over addition and subtraction

That’s what I needed , thanks anon.

>>9603913
>>9603934
Sorry, I don't mean to discourage or insult you. But I hope you are not a STEM student at university. If you are, you might consider dropping out or changing your major

>>9603587
Nowadays there are as many computer scientists as there are stars in the night sky.
If you like both biology and computer science, how about a bioinformatics degree?

>>9604004
I’m not, but I will eventually

>>9604045
I’m not a stem student but I will be eventually is what I’m trying to say.

>>9596221
If I lay on my back and all the blood in my brain goes to the back of my brain, does that enhance my sight because that's the part of the brain where sight functions?

>>9596277
Evolution you do
"If you believe in evolution, you've got to be a Nazi" - George Lincoln Rockwell

>>9597762
E=(kQ)/r^2

They are the same thing, right?

>>9604235
Not quite, they infer different axioms.

>>9596221
what would happen if out of nowhere venus and jupiter swapped places instantly?how about mars or the moon?

How do I go about solving this question?

>>9604600
Substitute e^(rt) for y and solve for r.

Hey Sci, I have to make an LZW decompressor for some test files having been given this as the brief for how they encoded it. I understand the general LZW algorithm and have written something that decodes based on the standard 256 char ascii table. Thing is I have no idea what these 12 and 16 bit widths actually refer to (not a comp sci grad/student) so have no idea how im meant to incorporate them for encoded data. Can anyone help a guy out?

>>9602540
it doesn't?

How do I do either of these?

>>9604628
What have you tried?

>>9604629

I've just been skipping the lectures this stuff was taught, so I need a little refresher.

>>9604606
samples of 12 bit size which is 4095 or something

>>9601607
Don’t you need an inverse of A in there?

Where do I start with this question?

>>9600565
try to meet people with those interest , they usually form groups at uni's

>>9600352
It’s a finite group generated by (2,5).
Parametric equation is k*(2,5). Probably other lines are k*(2,5) +j, one line per j.

>>9604744
Seperate the variables,
y on one side
x on the other
Then you just integrate both sides, using the chain rule to notice that d/dx[f(y)] = f'(y)y'

>>9596221
I'm a senior in high school (yes I'm over 18) and it hit me during these 4 years that I can't skate by on how smart I think I am. unfortunately I'm neither smart enough to actually skate by, nor did I work hard enough and now I just got rejected by UCLA. apart from the realization that I have no idea what the fuck I'm going to do in my life, and also that I realized I really don't want to go anywhere I've been accepted to and want to kill myself in this moment--

out of the following institutions what is /sci/'s opinion on the quality of each? I'm going for aerospace/mechanical engineering.

>San Diego State ( I got into honors there)
>Long beach state
>cal poly pomona
>University of Washington
>Texas A&M
>San francisco state
>Illinois Tech
>Purdue.

any thoughts on these universities, which has better programs/opportunities? any help would be appreciated, thanks.

In oxidative phosphorylation, why can't the FAD+ and NAD+ ions just take back the H- ions, why must O2 be the one to take it?

Brainlet here: is there an intuitive approach to the concepts of divergence and curl? I have been studying electromagnetics for more than a year and I still can't understand.

alright i have to be a fucking idiot here
so in a capacitor, current I=c*dv/dt
and the current through a resistor is V/R, by ohms law

and the sum of currents going into a node is the sum of currents leaving that node, by KCL

so wouldn't it make sense for at node N1 (ignore the wire under N1, i had to draw it so i could get a node point), sum of currents entering = sum of currents leaving?
I1=V/R and I2=c*dv/dt, therefore V/R = c*dv/dt, right?

i know that [math]\displaystyle V=V_0 e^{\frac {-t} {RC}}[/math] implies dv/dt will always be negative (although that equation is derived from exactly this problem, it also makes logical sense), whereas V/R will always be positive

however if you do KVL, you get Q/C = I1R, which makes sense because I1=V/R which is always positive

if i switch the arrow for I1 i'll get c*dv/dt + V/R = 0 for KCL which is correct, and for KVL i'll get Q/C + I1R = 0, which is incorrect
but if i fucking switch both arrows to point like that then the whole thing makes no sense: what fucking direction is the current flowing

what in the FUCK am i doing wrong

>>9605055
>I1=V/R and I2=c*dv/dt, therefore V/R = c*dv/dt, right?
I'm pretty sure you flipped the sign on your voltages. One of these should be negative.

>>9605106
I1=I2, I1=V/R, and I2=c*dv/dt
yes i know the real equation is c*dv/dt + V/R but i'm not understanding why

>>9605055
I haven't thought through the details, but be careful about the direction of the current and the potential GAIN of the capacitor and the potential LOSS of the resistor. If you are kissing a - sign, probably because of the difference of gain vs loss or from I being the rate of DISCHARGE of the capacitor being dq/dt and how this q is related to the Q on the capacitor.

>>9605126
You need to place V on an actual node and make the other one ground/0V. Don't just try to use the equations without relating them to the circuit diagram. Looking at and marking up the diagram helps you stay consistent.

>>9605134
alright let's let N1 be V and imagine N2 being at the top at 0V
I2=(V-0)/R = V/R like we had before
I1=c*dv/dt assuming the capacitor has a positive potential difference from N2 to N1
we still end up with c*dv/dt = v/r

if it doesn't have a positive potential difference from N2 to N1 then that wouldn't make sense, because current flows from higher potential to lower potential

what am i not seeing

>>9605171
>0 to V
>positive potential difference
fuck
yeah now i get it

Does the age of an applicant matter to employers even if they have professional/academic certification and a very clean record? I ask because I started college really late (27) majoring in Electrical Engineering and probably won't be ready to apply for entry level positions until I'm 31 or so. There are many reasons for this but it mainly boils down to a bad upbringing and now I'm just trying to salvage what's left of my life. I have this great fear inside me that I will get my degree, get all the certification, and when I submit my resume, the employer will contrast my age with my credentials and just toss my resume out. I'm doing all of my research and trying to do everything right but I can't make myself younger.

>>9605323
>>>/r9k/

>>9605323
it's really shit you'll miss out on some of your prime earning years of your life
also you'll have to explain the gap between high school and uni

as long as you take opportunities with research and internships you'll be fine

>>9604679
What does that even mean? D:

anyone able to help a brainlet
i know that once i orthogonalise these basis vectors that calculating the projection is trivial, but for whatever reason i cant orthogonalise them. ive tried using the gram-schmidt method and im sure im doing it correctly yet the vectors it returns to me arent orthogonal

>>9605609
>ive tried using the gram-schmidt method and im sure im doing it correctly yet the vectors it returns to me arent orthogonal
Show your work.

>>9605611
hopefully it's not indecipherable

>>9605618
I tried it using both vectors as my initial one and you can see neither worked out so there's clearly something wrong with what I'm doing

>>9605618
Re-read the projection formula.

how the heck do I construct a pencil of quadrics in [math]\mathbb{C}P^{2}[/math] such that the intersection of two quadrics in the pencil is equal to the three points [math]\{ [0:1:1],[1:0:1],[0:0:1] \}[/math]. PLEASE I HAVE NO IDEA I CAN'T FIND ANY EXAMPLES ANYWHERE.

>>9605609
desu I've never done gram-schmidt correctly by hand once in my life and I still got an A in linear algebra.

I wouldn't worry about it.

>>9596221
What the fuck is an energy level in chemistry.
What exactly is an orbital and what does it mean in terms of energy levels (if it means something).
When an electron "absorbs" a photon, what exactly is happening? Asked my chemistry tutor and they didn't know or couldn't communicate it.
Jesus Christ this subject is taught like shit. have learned far more from the textbook and youtube videos than the lectures and tuts.

So this is a weird question but why does water when mixed with limestone dust (either the calcium carbonate or calcium oxide) cause it to irritate skin worse than if no water was added?

>>9605700
An energy level is location of an electron relative to the nucleus. The more energy it has, the further away it is. Electrons aren't really in orbitals so much as clouds, but they're more probable to be along the orbitals you see in diagrams.
When a photon hits an electron, it transfers energy to the electron. This increase in energy moves the electron further away from the nucleus, putting it in the excited state. This excited state is not the most stable state, so the electron will emit a photon, lose energy, and return to the ground state.

>>9605700
>What exactly is an orbital and what does it mean in terms of energy levels (if it means something).

Orbitals are eigenvectors of the energy level which are the corresponding eigenvalue. Learn linear algebra.

>>9605762
>When an electron "absorbs" a photon, what exactly is happening

Its increasing in energy.

>>9598078
it's IQ you fucking imp

Here is a little thing for you:

AE = bisectrix of A.
AB = 14cm
Find CE and DE

Now, this is easy part.
Here is a hard one - find all the angles of both figures (triangle and parallelogram)

My progress so far:
/_CEA = 360 - /_A2 - /_D - 2*A2
but also /_CEA = 180 - /_AED = /_A2 + /_D
this will give us
180 = /_2A2 + /_D
got stuck here

How's N Pishkunov for Calculus?

Just bombed my phone interview, said so many filler worda like:: "like, um, but, things, stuff" and got asked about some programming language I have on my resume that I havent used for 5 years and said "i dont kniw what i did with that exactly" fuck...

adderall stronger than ritalin?

I want a serious, un meme answer to this question

is it possible a space elevator will be constructed this century?

>>9606765
No.

>>9605632
i dont know how i kept misreading it, i was going over it constantly becuase i knew i missed something

thanks bud

Need some help with some equations for HS chemistry (I'm a senior, just never bothered to take this class). I'm garbage at conversion and I can't find anything helpful online, so my only hope is that someone here has sympathy for a borderline retard and helps me out.

Anyways the question is asking me to find the frequency of the light being emitted by a proton with a wavelength of 493 nm, which I think would be 3.000*10^17 nm/s / 4.93 x 10 ^ 2 nm = 6.085192698*10^14 s, but my answer seems retarded so I have a feeling I went wrong somewhere with the calculation. Part B asks for the energy so I'm assuming it's my previous answer times 6.626*10^-24 J*s to which I got 6.0851926978 x 10^17 s x 6.626 x 10^-34 = 4.0320486816 x 10^-16 j^-1.

For the last question it's pretty much the same as the previous one except it's asking to find the frequency of the light being emitted by a proton with energy of 2.500J and to also find the wave length.

Can someone tell me if I'm going in the right direction and/or solve the second problem? Thanks in advance

>>9607339
sorry if this is a incoherent mess as well, wrote this in a hurry + im tired as shit lol

>>9607339
literally just check your units
>speed of light is m/s
>frequency is 1/s
>wavelength is m
>wavelength to frequency is m to 1/s which is just (m/s) / (m)
so 3e8 m/s / 493e-9 m = 6.08e14 1/s yes

>>9607366
>so 3e8 m/s / 493e-9 m = 6.08e14 1/s yes

Okay that's a relief. I'm so tired my brain is fucking lettuce right now, so it's taking me some time to do these. But anyways I went ahead and worked on the second one and got

2.500J/6.626*10^-34 J*S= 3.7730153939028 × 1033

and in order to find the wavelength you divide the speed of light by the frequency so

3.000 x 10^17 nm/s / 3.7730153939028 × 10^33 s = 79.512 × 10^-18 nm ?

Is it possible to prove Hilbert-Ackermann Axiom 4 with these axioms?

>>9605685
a x^2 + b x y + c y^2 + d x + e y + f = 0
x=0,y=0 --> f = 0
x=0,y=1 --> c + e =0
a x^2 + b x y + c y^2 + d x -c y = 0
x=1,y=0 --> a + d = 0
a x^2 + b x y + c y^2 - a x -c y = 0
a x^2 + b x y + c y^2 - a x z -c y z = 0

>>9596221
can acceleration in vector terminology be a concrete number. Like to find speed, youd have to find magnitude of velocity. Would magnitude of acceleration be the acceleration at a particular moment in time?

>>9607661
yes

Someone please help, I've done 3 classes where i've done image manipulation and my images always look like they've had some sort of filter applied.
I'm not really sure if I'm missing something in terms of getting a unsigned int and converting to double for calculations and then back to unsigned int for image display, is there some mathematics I'm missing?

is this a homogeneous linear differential equation
my notes say that a DE is only homogeneous if the dependent variable (y here) is raised to the first power, but its square rooted here which makes me think its not

can anyone confirm?

>>9607921
which equation?
am i supposed to read your mind or some?

>>9607947
tfw retarded

So in a compound like Lead (II) Sulfide, how do you find out that the equation is PbS? I know that Sulfate has a charge of -2, but how do I know Lead has +2?

>>9608190
Oh so I guess the roman numeral is an indicator of the charge, but then what about something like Zinc, which simply has a charge of +2?

Would it be wise to minor in math if my major is accounting?

I need assistance. Does anyone know the name of those black and white checker|line boards for visually measuring acceleration and velocity? I'm fucking retarded and legit need help with this.

>>9597081
Not him but from my experience in physics fairly minimal

How do i input 5 points into Wolfram in order for it to give me a fifth degree polynomial?

>>9608439
I'm waiting expectantly for an answer here

>"In 4 hours, motorboat, moving along the current, covers 10km less distance then in 6 hours against the current. Find the motorboat's own velocity if it is known that a raft on the same river within 15hrs covers the same distance as motorboat in 2hrs on a still lake"

>that feel when stuck for hours being unable to wrap my head around the fact that a full-speed boat covers less distance along the current than against it.
>that feel just cant imagine what a weird fucking velocity values there are to fit in 6:4 hrs difference

How do you find the position of nodes and anti-nodes using resonant frequency? The lab book I'm using has no explanation on how to do it.

>>9608190
>>9608195
If you're given something like Lead (II) Sulfide, you assume that it's in the neutral state (no net charge).
If not they'd give you something like [Lead (II) Sulfide]+
Here you're given that it's lead (II) and comes first in the name, you know wit has a positive oxidation state, and its charge is 2, so +2 for lead.
Since the compound is neutral, the sulfide must be -2, to balance out the +2 from lead.

Usually with these you start out with what you know for sure, like lead (II) definitely is +2, then you assign the other one such that it balances out and you have a neutral charge. As you've seen, many elements have multiple oxidation states.

>>9608439
>How do i input 5 points into Wolfram in order for it to give me a fifth degree polynomial?
Bad Idea.

I don't think Wolfram can do that, Matlab (and probably octave too) can:
http://reference.wolfram.com/language/ref/InterpolatingPolynomial.html

>>9608339
>>9608339
>>9608339
>>9608339
Really dumb question but I need to buy some of these, so I need help

>>9607921
>>9607953
basically a differential equation is homogeneous if every term includes the dependent variable. In this case, you have two terms y' and sqrt(y)cos(t), which both have a y term. So the ODE is homogeneous.
I think maybe youre confusing what it means to be homogeneous with what it means to be linear. An ODE is linear if the only y terms are of the form y, y', y'',... (or each term is only raised to the first power). Your ODE is non-linear precisely because of the square rooted term

>>9608789
> a differential equation is homogeneous if every term includes the dependent variable.
That isn't sufficient. For a differential equation to be homogeneous, the coefficients of the dependent variable and its derivatives have to be homogeneous functions, i.e. f(k*x)=k^n*f(x).

>>9608502
You'll have to have information about the boundary conditions of the waveform. What I mean is: are there nodes or antinodes at the end points? Also, you need to know the speed of the waves in question and the number of nodes.

Due to their electron structure, can transition elements form up to 6+ bonds, or does the 4s subshell hybridizes with the 4d one instead?

I want to study cosmology but I don't know where to start.

I've tried to research some suggested books by the college courses but they seem to differ greatly.

Does anyone know any good course online or set of books?

thanks in advance

>>9596277
If they loved science they wouldn't be far-right anon

>>9608439
If you want a sort of "Easy Mode" way to do this, just use a Lagrange Polynomial:

http://mathworld.wolfram.com/LagrangeInterpolatingPolynomial.html
https://en.wikipedia.org/wiki/Lagrange_polynomial

>>9609140
No, that can not work, at least it won't work until you add another arbitrary point.
They question is entirely ambiguous, there are an infinite number of polynomials with degree 5 for 5 points.

Lagrange polynomials will ALWAYS have degree <= (n-1) for n data points.

He should probably solve a least squares problem, or something like that.

>Let |G| = pq. By Cauchy’s theorem, G has an element a of order p and an element
b of order q. If G is abelian then ab has order pq, so G is cyclic.
Can somebody fill the gap on the last bit? Abelian doesnt imply cyclic, and Cauchys group theorem is just "if p divides |G| then there is a group of order p in G"
Im not sure how that leads to cyclic

>>9609157
My bad. Misread the question.
Just saw the word 'interpolation" and got 'Nam flashbacks to my scientific computing class.

>>9609174
if a group of order n has an element of order n then the group is cyclic

How the hell am I supposed to solve this?
No other information is given.

>>9609386

I've just been trying with spheres, is there a nicer way to prove that all [math]\mathbb{R}^n[/math] isometries are repeated reflections? Particularly for when n is 2 and 3.

>>9602210
I think you mean the set of all sets that do not contain themselves.

https://en.wikipedia.org/wiki/Russell's_paradox

>>9604487
can you elaborate?
it seems to me that the two sets are equal

>>9609564
The isometry group of R^n is O(n).

>>9609157
You're right, i had to pick a 6th point to make the polynomial

Why aren't other animals as intelligent as us?

>>9609174
>>9609245
So
>G is order pq
>Cauchy's Theorem states there are then elements of order p and q in G
>Lagrange's Theorem means there are q many elements order p, and p many order q
>Abelian means we can take elements a order p and b order q to get ab
>ab has order pq
>G is order pq with element ab order pq and so G is cyclic order pq
Or am I doing this wrong

I'm currently sitting in Calculus II feeling like a moron.
It's been 2 years since I took Calculus I and 6 years since I took collegiate algebra.

I remember most of the calc 1 stuff, since it was just basic derivatives and integrations, but I feel like I'm being fucked hard by the algebra.
I talked to my professor about it, and he agreed, saying "algebra is the hard part of calculus."

Any book recommendations for collegiate algebra?

Is working memory entirely genetic or can it be developed? Is there an age limit to when it can be developed? Is there a limit to how much it can be improved?

>>9609964
Calc2 is just Calc1 in reverse.

>>9596221
When should I stop an iterative root-finding algorithm?
In my program I used the definition of a root: [math] \text{while} \ \left( f(x_n) > \varepsilon \right) [/math] and the teacher said it was ok. But then I though, what if the function changes REALLY slowly? So slowly, that it ranges from [math] -10^{-6} [/math] to [math] 10^{-6} [/math] over a 1000-unit-long interval?

>>9610126
depends on the algorithm and your needs

>>9609992
Working memory is a bullshit science and psychology is all fake.

>>9609623
That doesn't include translations, although I suppose I could just reduce things to [math](F(x)-F(0))+F(0)[/math].
I'll try and work with that.

stupid questions you say?

Is there any plausible way to explain a naturally occurring phenomenon that would cause local intermittent EMPs?

> crazy and stupid i know, basically im trying to write a story where the lights keep going out for minutes at a time in a small isolated town and wanted a scientific reason to explain it

Is this living? Or is this just torture?

Is Arnold's ODE good?

>>9610599
>Is Arnold's ODE good?
Read it and find out.

define [eqn]f(x)=\begin{cases}0 & x=0 \\ 1 & x\in (0,1]\end{cases}[/eqn]
[math]U(f,P)=1[/math] for any partition on [math][0,1][/math] right? [math]\displaystyle \sum_{k=1}^{n}M_{k}(x_{k}-x_{k-1} )=\sum_{k=1}^{n}(x_{k}-x_{k-1}) = 1-0 =1[/math]?

Is there a type of concurrency which is generally faster than the other types? I'm thinking of ExecutorService vs blockingdeque fx. This is of course for Java.

>>9597016
A histone is basically a blob with a tail. DNA wraps around the blob, and histone tail modifications mark certain parts of the tail. The modifications attract chromatin remodeling complexes, which then fuck with the larger structure of the chromosome.

Ring theory question:

Part (a) is obviously trivial but I am not really sure how to do (b). Prof glossed over indecomposible decompositions of rings very quickly in the lecture and I didn't quite understand. How does the partial fraction decomposition aid in doing this?

>>9610950
Every finitely-generated torsion module over a PID decomposes as [math]V \simeq \bigoplus_{k=1}^n R/(\delta_k)[/math] where [math] \delta_1, ..., \delta_k[/math] are prime powers in [math]R[/math]. Hence the summands [math]R/(\delta_k)[/math] are indecomposable. Your module is annihilated by [math]x^3-3x-2[/math], so finding its decomposition is equivalent to finding the prime factors of [math]x^3-3x-2[/math].

>>9596221
How to live?

>>9596963
late af but here you go:
being a manifold is structure of its own, so if you want a manifold that is also a group then just equip the underlying set with both structures: take whatever manifold data you need, usually a Hausdorff + second countable + locally Euclidean topology [math]\tau\subseteq2^{2^M}[/math], and also take whatever group data you need, usually multiplication [math]({\cdot}):M^2\to M[/math] and inverse [math]({}^{-1}):M\to M[/math] and identity [math]1\in M[/math].
almost certainly you want these structures to be somehow compatible, too, so you also ask that e.g. the multiplication and inverse maps are continuous or smooth or whatever.
that's it, no magic

>>9611246
by which i mean [math]\tau\subseteq2^M[/math] ofc

can someone help me solve this? i have to find the total impedance between A and B

>>9611111
>How to live?
not science or math

>>9611471
So science says “Kill yourself"?
There is biology, psychology, medicine, neuroscience, applied math, computers that can do many things and maybe economics.

Anyone want to verify the answer to this question? I got 6

>>9611103
alright, I got it. thanks!

>>9611734
that's not the correct answer

>>9610777
it's been a while since i did this, but M_k is the supremum over the k-th interval, right?
Then i think youre right since f is an increasing function so [math]\sup(f(x):x_{k-1}\leq x\leq x_k)=f(x_k)=1[/math]

https://arxiv.org/pdf/1205.2204.pdf

First, the integral they use to get the Shell Method is incorrect isn't it? The inside of the integral should be 2pix(f_1(x)-f_2(x)) right?

Secondly what is Fubini's theorem?

Lastly if can someone show me an example of them using the double integral described by the paper to calculate something like some bounded area being rotated around a line that isn't parallel to either the x or y axis. Like around the y=x line or any other straight line?

>>9612019
>Secondly what is Fubini's theorem?
https://en.wikipedia.org/wiki/Fubini's_theorem

>>9612019
https://arxiv.org/abs/1205.2204
Link to the Cornell library that has the abstract.

>>9612021
What does the variable at the bottom of the integral mean? Is it just redundancy to dx or dy?

Is it weird to ask your math professor for academic advice? Or questions about his PhD research? I've decided to major in math and I'd like to talk to my professor first as opposed to an academic advisor who doesn't know shit about the major. He seems to like me since I am doing pretty well in the class. He's a young guy which gives the illusion of him being more approachable. My bad if this is a dumbass question I just don't like one on one meetings and I don't know if this would be appropriate.

>>9612137
I mean what's the worst that can happen? He doesn't want to answer so he says sorry I don't have time right now to be polite?

How do I "get" math?
Calculus has felt like just memorizing a bunch of arbitrary rules. I don't know how they piece together or what their purpose is.

I want to know the "why."
I want to understand these problems and their solutions, not just regurgitate a memorized strategy.

>>9612207
Read the textbook. If you're still lost find some supplementary sources that do a better job of explaining things more intuitively. That's what I did.

>>9612207
Learn how to do proofs, then read a ton of proofs, then try to prove previously unseen theorems without reading the proof first until you get it.

>>9612207
3Blue1Brown videos on the essence of calculus really good source.

>>9612232
Maybe my textbook is shit, but it doesn't explain the "why"; it just has bullet points for formulas and strategies for solving equations with particular attributes.

>>9612254
I have a basic understanding of formal proofs. I took a course on discrete math that I thoroughly enjoyed, and proofs were a component of it.

>>9611471
You're wrong. Math is, in it's purest form, how man tries to understand reality.
If there is one discipline able to answer that question, it would be Math

>>9612207
Look for practical applications of it. Proofs will only show you that the math is sound, not really the why.

>>9612299
>Math is, in it's purest form, how man tries to understand reality.
Wrong.

Does a rational number only mean it can be written as the fraction of 2 integers? Or can it be the fraction of any 2 real numbers?

>>9612532
integers

>>9612568
So does that mean pi could be represented as the ratio of 2 non-integer rational numbers?

If Einstein did that whole thing with the relativity of simultaneity, by what frame of reference can events involving quantum entanglement be considered concurrent?

Less a stupid question and more one i'm too drunk to convey coherently.

>Due date: March 23
It's already midnight here and I'm still not sure about my answer to 1a. College was a mistake lads

>>9612583
Physicucks arent allowed in this thread

>>9612571
>So does that mean pi could be represented as the ratio of 2 non-integer rational numbers?
Yes, pi/1

>>9612571
no, if a number can be represented by the quotient of two rational numbers than it can be represented by the quotient of two integers by extension.
>>9612591
pi is not a rational number

>>9612532
>Or can it be the fraction of any 2 real numbers?
Any real number can be written as the fraction of 2 real numbers.
A rational number can be written as a ratio of integers.

>>9612571
No, any ratio of two rational numbesr is, by definition, a rational number again.

>>9612137
Why would it be weird? I have yet to come across a professor who would respond negatively to someone showing interest in his research.
The worst that could happen is him being in a hurry and you not getting an answer.

>>9612029
>What does the variable at the bottom of the integral mean?
It is the set over which you integrate.

>>9612349
You can't just say "Wrong" and input nothing else.

a+b = 6
ab = 9
a = 6-b
b(6-b) = 9
6b - b^2 = 9
[math]\sqrt{6b}-b=3[/math]

I know that a and b = 3 but HOW

>>9613421
If you take the square root of 6b - b^2 = 9 you get sqrt[6b - b^2]=3. you can't just solve the square root of 6b and - b^2 individually like that

>>9613442
What? Why? it is a simple linear equation. Consider this:

4a + 2b = 12 | /2
[math]\frac{4a}{2}+\frac{2b}{b} = \frac{12}{2}[/math]
==
2a + b = 6

We divide each member of the equation by 2 to keep things equal

Same here:
6b - b^2 = 9
we square root every member therefore equation is balanced
[math]\sqrt{6b} - \sqrt{b^2} = \sqrt{9}[/math]

>>9613469
there should be 2b/2, typo

anyway, I realized i fucked up :

9 - 2^2 = 5

fucking sqrts and power mess my head

>>9613442
anyway, even so, how do you fucking solve

[math]\sqrt{6b-b^2} = 3[/math]?
b is 3 but fucking how

>>9613469
No, that is not how square roots work.
It's very simple to check.
[math]1+1=2[/math]
[math]\sqrt{1}+\sqrt{1}=1+1=2\ne\sqrt{2}[/math]

>>9613480
[math]ax^2+bx+c=0\iff x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}[/math]

>>9613501
ok thanks makes sense
clearly the puzzle was intended to be solved via intuition since square equations not part of the topic

>>9613469
No, that is not it. Since it's a subtraction you must do what is inside the square root first. If it was a multiplication it would be fine however.
I'll have to link you to basic math properties
https://en.wikipedia.org/wiki/Associative_property
>>9613480
Bhaskara's Formula

>>9596221
https://www.youtube.com/watch?v=oMTBbVn-bnA&feature=youtu.be

>>9613538
>mfw being this afraid of death and so delusional you waste the rest of your life on this hoping the magic elixir will be developer in time

I mean dying issuck but come the fuck on

Does anyone know if its possible to use k-means clustering to identify confounding groups (like the ones in the graph) for regression analysis?