/sqt/: Stupid Questions Thread

If I'm doing an exam in quantum mechanics, will the answers to previous problems change when I answer the final problem?

>>8541022
Depends on whether you check your work or not.

>>8540979
[math]w_k^TS_tw_k = tr(w_k^TS_tw_k) = tr(w_kw_k^TS_t)[/math]
then bring the sum back into the trace and define [math]WW^T = \sum_{k=1}^d w_kw_k^T[/math]

>>8541145
Yeah I'm dumb I didn't realise [math]W^T_kS_tw_k[/math] leads to trace. thanks anon

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Anyone knows how the second term came to be? If I open the brackets, yeah I get [math]X^TX[/math], but how did they get to [math]W^TXX^TW[/math]?

How do I revise lads. Got my notes I made, the teachers notes, practice questions in front of me atm I'm reading my and their notes and ever so often spewing it back to myself feels passive AF.

(x^(1/2) - 4)/(x - 16)

This problem looks so simple but I have no idea how to simplify this expression. Help?

>>8540979

Wolfram can't figure out this shit.

{1, 30, -2, 71, 1, 1, -132, 490, 23}

Could you using interpolation?

My retardation precedes me.

>>8541517
Don't you think that root(x)-4 and x -16 look awfully similar?

The solution is (1/(root(x)+4))

>>8541555
Yeah, I know but I don't know what method I should use for these problems. For example, here's a harder one:
[math](x-8)/(\sqrt[3]{x^2} + 2\sqrt[3]{x}+ 4)[/math]
Can you show me how you would solve this?

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I'm nearsighted and I need glasses to use the computer. Now I'm doing it without glasses. I bring the monitor forward, close enough where I can just barely make out the letters without squinting or straining my eyes, and I fell like, if I will do this for long enough, that my sight will improve. Am I wasting my time with this?
pic related, me atm

>>8541577
Good job, you are retarded, son.

>>8541594
You got a better plan?
I've been wearing glasses non stop for the past 8 years and I have to change lenses almost every 2 years because my sight is getting progressively shittier, and just now I'm starting to think that it might be the glasses fault.
There's an entire industry behind this shit, why wouldn't they want to make me lose my vision, just so I have to buy new glasses all the time.

Can someone explain what the hell is "residual porosity" ?

I can't find any explanations for it, I'd really appreciate the help.

What's a good Master's Degree to get once I get my BSc in Math?

>>8541609
Sorry, I can't help you. You are past the point of redemption.

can someone either explain basic NMR to me, or link me something that can help. My O chem final is later today, I that's the only concept I can't wrap my head around

>>8541623
intensity - number of equivalent protons
multiplicity - number of equivalent neighbour protons, where singlet=0, doublet=1, triplet=2 and so on

the more electronegative a proton's surrounding is, the more it gets shifted to the left
tables of chemical shifts can be easily found in google

does there exist a polynomial bijection from QxQ to Q?

>>8541564
Fucking hell. That one was really tricky because I didn't know binomials very well.

All you have to do is know all the binomial formulas and look at what you are given. In this case you have the third root, so you need a binomial of grade 3 most likely.

Look up a^3 - b^3. The equation you have is given in the form (a^3 - b^3)/(a^2 +ba +b^2).
Solution is third root of x minus 2.

>>8541577
>Am I wasting my time with this?
Yes. The eye is not a muscle. While your sight can be corrected, it's not like this.

>>8541935
Okay, I managed to solve a few problems and I think I get it now. Thank you.

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Prolonged zero gravity can really fuck up your body. Decreased bone density and muscle mass, accelerated Alzheimer's, decreased RBC and immune system, blood pressure and fluid redistribution.

Are there any positive health effects? Specifically for women, would a month or more in space be enough to have a permanent and positive effect on sagging boobs? Since it's caused by gravity, zero G would give the body could give the body time to heal and repair drooping boobs. Also, fluids tend to get redistributed in zero g, so should boobs get bigger too?

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>>8541577
>>8542004
>The eye is not a muscle.
The eye does have muscles in it that help you focus and there are ways to strengthen them. Stenopeic glasses are lenses totally opaque with tiny holes in them. It's been proven to improve eye sight while wearing them and over time, improve eye sight while not wearing them. It's thought to be from training those muscles, but nobody is really sure how the glasses work.

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Where does the +1 come from? Please help, I have final tomorrow

if R and S are posets of X is R intersect S a poset?

>>8542152
-(-9/4)^0 = -1

>>8541577
if you start using glasses your eyesight will get worse much faster

if you don't want glasses you're probs not wasting ur time

This is an really specific question but how can I practice translating concepts/sentences into algebraic equations?
I mean translating as in making equations off this sentence to solve the riddle.
"A princess is as old as the prince will be when the princess is twice as old as the prince was when the princess' age was half the sum of their current ages."

>>8542298
thats one of the most poorly constructed sentences ive ever seen

Let n > k > 2 be natural numbers. I have a set of n elements from which I wish to generate k-sized subsets such that no two subsets share 2 or more elements.
What is the maximum number of subsets I can generate this way?

Why can't I remember things?

I feel like I have a concept down decently while doing practice problems with steps I can look to for guidance, and even doing problems after that with no guidance I feel like I at least know what to do.

But one or two weeks later and I don't remember it at all and fail tests.

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I somehow slipped through the cracks when transferring my math classes from my college and I'm taking ODE with no knowledge of series from calculus. Am I fucked?

>>8541527

Stupid bump

>>8542414
you didnt even ask a question, you just listed a set

redpill me on being a chemical engineer.

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I'm not really following this, does anyone care to explain it to me in simpler terms (if possible).

Damn I feel like a brainlet

>>8542643
Remember when you did whole number division in elementary school, and your teacher would give you 27/5 and your answer would be 5 remainder 2?

This is exactly what they're doing. You find the biggest multiple of 5 that divides 27 and then subtract to find the remainder that's left.

There's a bit of work involved in proving that 0<=r<5, but it should be pretty intuitively obvious that your remainder can't be negative or bigger than the thing you're dividing by.

>>8542691
So, in a=qb+r...
>a = the number you're dividing
>q = one number
>b = highest multiple of that number that divides into the original number
>r = remainder

correct? I still don't really understand the set that they made and the point of doing so.

>>8541921
tough question desu

http://mathoverflow.net/questions/21003/polynomial-bijection-from-mathbb-q-times-mathbb-q-to-mathbb-q

When finding the scalar potential of a vector field, how does integrating the components work?

Let me rephrase that. So to find the scalar potential, we would say that the vector field F = Mi + Nj + Pk, and (grad f) = \partial M /\partial X, \partial N / \partial y, etc...

To find f, we would integrate \partialM/\partial X with respect to X.... Can we do that? Like, can we integrate a partial derivative with respect to X? Sorry if my question doesn't make much sense, I don't really know that much about multivar

>>8542298
> "A princess is as old as the prince will be when the princess is twice as old as the prince was when the princess' age was half the sum of their current ages."
Work backwards, and remember that the difference between their ages never changes.

Current ages are x (princess) and y (prince).
When the princess' age is A, the prince's age is A+(y-x)

Half the sum of their current ages = (x+y)/2
Prince's age when the princess' age was that = (x+y)/2+(y-x)
Twice that age = (x+y)+2*(y-x) = 3*y-x
Prince's age when the princess' age will be that = (3*y-x)+(y-x) = 4*y-2*x
Which is the princess' current age: x = 4*y-2*x => 3*x=4*y => y=(3/4)*x.

The only option on the list which satisfies that is the princess is 40, the prince is 30.

>>8542331
First, if n < 2k, then it's zero.

Otherwise, there are C(n,k) = n!/(k!(n-k)!) ways to choose one subset, and C(n-k,k) ways to choose a second, resulting in C(n,k)*C(n-k,k) ways to choose an ordered pair of subsets. If you don't care about ordering, then halve that.

For m subsets, then it's C(n,k)*C(n-k,k)*C(n-2k,k)*...*C(n-(m-1)k,k) ways to choose an ordered m-tuple; divide by m! if you don't care about ordering.

>>8542791
[math]\int \limits _{C}\mathbf {F} (\mathbf {r} )\cdot \,d\mathbf {r} =\int _{a}^{b}\mathbf {F} (\mathbf {r} (t))\cdot \mathbf {r} '(t)\,dt[/math]
IOW, you first need to parameterise the curve (express it as a function from R->R^n). Then you can integrate the dot product of the vector field and the curve's tangent w.r.t. the parameter.

Note that a vector field only /has/ a scalar potential if the integral depends only upon the endpoints, regardless of the rest of the curve. In turn, this implies that the vector field is the gradient of a scalar field, which means that its curl is zero everywhere.

>>8542791
Yeah, actually exactly as you described it.

>>8542845
That's not his fucking question, but true.
He's saying, I have this vector field
[math]
\mathbf{F}
[/math]
with 0 curl, and knowing this, I want to find a scalar potential. To find this scalar potential, we effectively just have to do a "partial integral" with respect to each variable.

>>8542845
Conversely, if the field does have scalar potential, then it doesn't matter which curve you use, so you can just use a line segment, r(t) = p0*(1-t)+p1*t = p0+t*(p1-p0) => r'(t)=p1-p0.

So you can just take the component of the field in the direction of the line and integrate that.

Or you could use a piecewise curve where each piece is axis-aligned.

>>8542791
kind of. you want to find f so that f_x=M, f_y=N, f_y=P. So the first step would integrating M with respect to x. But you have to be careful with the constant of integration.

when you do a single variable integral, you need to add a +C because dC/dx=0 so the derivative can't "see" the extra constant.

In this case, when you integrate with respect to x, the "constant of integration" is really an arbitrary function g(y,z) of y and z, since the x-derivative of this is zero.

So f=integral(Mdx)+g(y,z), but you have no idea what g is. To solve for g, take the y-derivative of both sides and set it equal to N. Now try to take it from here.

i'm starting calc 1 next semester and i'd like a leg up
for someone who just finished pre-calc what should i study to get ready?

>>8542884
Professor Leonard on youtube.
I can guarantee you will get no less than a b if you watch his calc 1 series.

>>8542902
thanks!

>>8542824
I think you misunderstood the question. I'm not talking about how many ways there are to generate the subsets, I'm asking how many can you possibly generate given the rule.

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>>8540979
Anyone able to help me figure out how to get to the answer?
The correct answer is A.

My method:
dI = dm*x^2
dm = 2M/D * dx (2 dots fit in each triangle)

dI = 2M/D * x^2 dx

I = 2M/D * Integral: x^2 dx
I = 2M/D * Integral: (D/sqrt(2))^2 dx
I = 2M/D * 1/6 * D^3
I = M/3 * D^2

Any help?

>>8543072
M/3*D^2 is closest to A among the available options, so it looks like you've already solved it.

>>8543091
Is that actually what they mean? That seems absurd. Would they not put the exact answer up there?

>>8543072
2R^2 = D^2
2mR^2 = mD^2

>>8543072
A. It's just 2*m*r^2 = m*D^2 (as r=D/sqrt(2)).

Why are you integrating? it's just two point masses (the ones on the axis of rotation are irrelevant).

>>8543199
I want to know how to find this stuff out through integration, likely the actual test will be harder.

I genuinely do not understand basic combinatorics.

If there are 3 boys and 5 girls seated randomly in a row, can someone point me in the direction of how to find the probability that the boys are side by side and the girls are side by side?

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Why is x = 1/5, y = -1/5, and z = 2/5
Is it because x appears 5 times in total?

>>8543264
I'm not sure what you're asking, the results are pretty straightforward if you just solve the system through elimination.

>>8543260
There are two ways for this to occur: all the boys on the left or all the boys on the right. Next, there are 7 choose 3 possible arrangements of the the line (out of the 7 seats, you choose 3 to put boys in). Thus, the probability is 2/(7 choose 3) = 2/(7!/[(7-3)!3!]) = 2/35.

>>8543291
Well, thanks for trying but the solution key has the answer as [(2!)(5!)(3!)]/(8!), which reduces down to 1/28. It doesn't say how to get to that fraction of factorials though.

>>8543301
For some reason I decided 3+5 = 7. If you replace 7 with 8 in my explanation you get the right answer.

>>8543306
Oh duh, thanks man!!!

>>8543291
Did you mean boys are side by side AND girls, or either of the two?

I have a digital systems exam soon, any tips? I hope I can remeber how to do counters and basic shit. Also the fucking delay stuff is weird.

A motor boat needs a hours to go from A to B
down the river and n
eeds b hours to go from B to A (up the river) .
How many hours would it need to go from A to B if there were no
current
in the river?

Is bioinformatics a good field to get into if I want to solve interesting problems using programming?

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Help, please. My answer is (v1+v2)/2, but I feel like its not correct

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>>8543455
Seems right to me

>>8543455
It's (2*v1*v2)/(v1+v2)

>>8543479
what

>>8543249
Integration is only relevant when the mass is distributed over a volume with finite density.

For a point mass, it's just m*r^2.

For a volume, it's the sum of infinitely many infinitesimal point masses, i.e. an integral (in the most general case, a triple integral).

>>8543483
You cover the first half of the distance m in t1 = (m/2)/v1, the second half in t2 = (m/2)/v2.

with t = t1 + t2, the mean velocity v is a weighted mean like so:

v = v1 * t1 / t + v2 * t2 / t

Which is (2 * v1 * v2) / (v1 + v2)

>>8543483
If the distance between the two points is D, the first half of the trip takes time D/v1, the second half takes time D/v2, the total time is D/v1+D/v2 = D*(v1+v2)/(v1*v2), the total distance travelled is 2*D, so the average speed is 2*D/(D*(v1+v2)/(v1*v2)) = 2*(v1*v2)/(v1+v2).

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Doing basic theory, and just to make sure, the notation a' means the inverse of a, right?

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>>8543576
>theory

group theory :-)

>>8543260
Hey anon, /lgbt/ here!
In the spirit of being politically correct, please use Xes and Xers in place of boys and girls next time. Thank you!
:^)

>>8543576
No, that's only true for abelian groups
In general, (ab)' = b'a'

>>8543581
To add: They might be using the ' notation to denote some homomorphism

>>8543486
I see, thank you

>>8543576
thats obviously a prime meaning the derivative of a :)

>>8543581
Aite, thanks. Does it have a name for non-Abelian groups?

>>8543612
You mean the ' operation?

Like I said here >>8543588 it's possible that they're using it to refer to some group homomorphism (a map which preserves the structure of the group) F: G -> G', with g' written in place of F(g), so that
F(ab) = F(a)F(b) becomes (ab)' = a'b'

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>>8543623
>homomorphism

haha homo :-DDD ebin u algebraists are so fucking gay lmao@u

But alright, thanks man, appreciate the help :-)

Which of these options is better for career prospects:

1) get a PhD from a top university but don't publish anything particularly interesting before graduating

2) get a PhD from a low-to-mid-tier university but score a few high-impact publications during your PhD

?

[math]\color{#781b86}{\text{Do}}\color{#511da7}{\text{n'}}\color{#4136c0}{\text{t }}\color{#3e56cd}{\text{mi}}\color{#4274cd}{\text{nd}}\color{#4b8dc1}{\text{ m}}\color{#57a0ad}{\text{e }}\color{#66ae94}{\text{ju}}\color{#78b67c}{\text{st}}\color{#8ebb66}{\text{ t}}\color{#a5bd55}{\text{es}}\color{#bbbb48}{\text{ti}}\color{#cfb440}{\text{ng}}\color{#dea53b}{\text{ s}}\color{#e58e36}{\text{om}}\color{#e56e30}{\text{et}}\color{#df4828}{\text{hi}}\color{#da2121}{\text{ng}}[/math]

[math]\color{#781b86}{\text{I h}}\color{#671c94}{\text{ave}}\color{#571da2}{\text{ re}}\color{#4c23ae}{\text{fin}}\color{#462eb9}{\text{ed }}\color{#3f39c4}{\text{my }}\color{#3f47c8}{\text{rai}}\color{#3e55cd}{\text{nbo}}\color{#3f62cf}{\text{w c}}\color{#416fce}{\text{olo}}\color{#437ccc}{\text{rat}}\color{#4786c6}{\text{ion}}\color{#4b90bf}{\text{ al}}\color{#5098b7}{\text{gor}}\color{#56a0ae}{\text{ith}}\color{#5ba7a4}{\text{m t}}\color{#62ab99}{\text{o a}}\color{#6ab08f}{\text{cco}}\color{#71b484}{\text{mod}}\color{#7ab77a}{\text{ate}}\color{#82ba70}{\text{ st}}\color{#8cbb68}{\text{rin}}\color{#96bc5f}{\text{gs }}\color{#9fbd58}{\text{of }}\color{#a9bd52}{\text{muc}}\color{#b3bd4c}{\text{h l}}\color{#bcbb48}{\text{ong}}\color{#c6b844}{\text{er }}\color{#ceb541}{\text{len}}\color{#d5b03e}{\text{gth}}\color{#dcab3c}{\text{ at}}\color{#e0a23a}{\text{ th}}\color{#e39938}{\text{e c}}\color{#e58e35}{\text{ost}}\color{#e68033}{\text{ of}}\color{#e67330}{\text{ a }}\color{#e3632d}{\text{bit}}\color{#e1522a}{\text{ of}}\color{#de4227}{\text{ qu}}\color{#dc3124}{\text{ali}}\color{#da2121}{\text{ty}}[/math]

If f: [0, 1] → [0, 1] is a continuous function, how do I prove that there must exist a fixed point t for which f(t) = t? I know that [0, 1] is connected, and if g(t) = f(t) - t and no t exists so that g(t) = 0 then that probably would imply [0, 1] can be split up into two open sets, resulting in a contradiction. I just cant seem to fill in the details though.

Is there anyone who understands main/interaction effects in statistics?

We had a test recently in which we had to analyse two models on R to explain variation in a variable (petal length). One model explained petal length as a response to variation in petal width and flower species + interaction between the factors, while the other explained it purely as a product of variation in petal width.

The first model (Petal.Length~Petal.Width*Species) was significantly better because species had a significant effect on petal length and explained most of the variation. There was however no significant effect of Petal.Width:species interaction on the response variable.

The correct answer to a question in the test states that "Model 1 is better than Model 2 : the dependence of petall length on petal width varies by species"

Isn't this bullshit?
I mean it sounds like it's talking about an interaction effect to me in that answer because it's saying that the relationship between petal length and width varies by species which it doesn't. Petal length itself does vary between species INDEPENDENT of petal width though.

Can anyone help me

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pls help a brainlet

>>8544136
just consider the function g(x) =f(x)- x. it is continuous and g(0)>=0, g(1) <=0
then g(x) has a root somewhere

>>8544158
just add 9 to every function and do the classic solid of rotation integrul integrul

>>8544165
i don't understand ;_;

>>8544176
the axis is at y=-9
to make things easier just translate it to y=0.

draw it

>>8544158
Imagine that you create a cylinder from revolving that region about -9

You can find the volume of infinitesimally small cylinders at a particular point and sum then to find the volume.

V = 2π(radius)(height) ; cross sectional area.

Find the radius and height

If a tautology is something that's true in all possible cases, how can we find a case where a disjunction 'p or not p' isn't a tautology, namely if three valued logic applies, and then still have people claiming it's a tautology? The mere possibility of it being wrong should stop it from universally obtaining. I must be missing something.

>>8543750
Well I'm willing to bet that the name of your advisor and school matter, but not to the point of making up for a lack of interesting work altogether.

>>8544136
https://en.wikipedia.org/wiki/Brouwer_fixed-point_theorem

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taking algebraic topology next semester and two main topics are the ring structure of cohomology and the poincare duality theorem

i've found a handful of ring structures i want to get comfortable with computing, are there some important concepts i should check out that come through poincare duality?

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How many species in Lepidoptera have eyespots?
/an/ said 654 or 655, but didn't give a source. Do you have an answer?

>>8544712
that's a pretty obscure question why do you need to know

How should I use matrices to handle rotation and position of both an object and a viewpoint in three dimensions?

I had a go at it in a program, and it turned out sort of okay, but it's still kind of a mess so I want to see how better mathematicians do it.

how do i make the ultimate dankest formula?

>>8544751
For a paper. I couldn't find the answer online. Searching "lepidoptera eyespot species number" gives no dice whatsoever.

>stupid question thread
>most questions remain unanswered

brainlet here

what do they mean by this?

"Recall that the mole fraction of C2HCl3 in the vapour phase is equal to the partial pressure of C2HCl3 divided by the total pressure. Use Raoult's law to write an equation for the partial pressure of C2HCl3 and an equation for the total pressure. Divide these equations by each other and solve for the mole fraction of C2HCl3 in the liquid phase."

>>8545040
The problem is, people keep asking open ended questions that really do deserve their own thread.
Also, it's very rare that a question which has been replied to with a non-answer will get an answer, because people habitually ignore questions with replies since they look answered.

While most of the time I think 4chan is overmodderated, there really needs to be a rule against posts like >>8544751 because it's completely pointless to give non-answers and forces the question to be reposted.

>>8545045
nevermind, I got it

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>>8544176
If you still don't get it, this probably won't help you either :)

>>8545168
>tfw taking calc 1 final tomorrow
>will probably fail it and then that will cause me to fail the class

;_;

>>8545173
You should be studying right now m8, or rather earlier? What don't you know how to do?

>>8545178
I was just doing a thing for it. I basically don't really know how to do anything that well, I just know that for some stuff I can use a formula and find the answer. I can do basic stuff for most of the thing you do, like finding volumes and stuff but I can't do anything complicated and usually just have to memorize it as a series of steps. I don't really have an understanding of what I'm actually doing which would help me do better.

Oh well, hopefully I can make a good note sheet and pass the class with a C, although I got a 55% on the last exam so probably not.

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>>8545187
Yeah rip then, wouldn't exactly call that complicated but you'd need the fundamentals to do shit. Like you probably won't be able to graph a rational function. If you can at least differentiate and integrate then you could do alright. And if you don't understand those then you're fucked. You still have a little time to maybe cram hard

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How would I go about resolving the curl of a surface vector field in terms of the surface tangent vectors and normal vector?

I tried just plugging the vector components into the general formula for curl in curvilinear coords, but that equation has three indices (i,j,k) and the surface cross product only seems to have two (α,β). The answer key gives a linear combination of the curvature tensor components and the surface tangent vectors plus a linear combination of the Christoffel symbols and the unit normal vector. Some fucking how.

Help a stupid fucker out

>>8545195
Yeah, hopefully I don't fail it but if I do then maybe I can actually take it in person instead of one of the shitty online-only everything through mymathlab thing that I did with it this semester.

Idk what it is, I do well and understand stuff in other subjects but it takes me a lot more time and I have to practice a lot to understand math.

>>8545208
definitely not enough time to learn that shit, but https://www.youtube.com/playlist?list=PL58C7BA6C14FD8F48 and https://www.youtube.com/watch?v=fYyARMqiaag&list=PLF797E961509B4EB5 and http://tutorial.math.lamar.edu/Classes/CalcI/CalcI.aspx

>>8545218
Eh, it's over Applications of Derivatives and Integrals, and Integration.


I'm making notes now or something but it's almost midnight here and the test is at 9am tomorrow, so I don't have whole lot of time. I'll probably just finish notes and try to go over practice quizzes for the chapters.

Physics problem here, I've tried everything i can but i just can't see how to solve this.

So an explosion breaks a rock at rest into three pieces, first weighs 0.5kg and is sent flying 2m/s in the X dimension, second weighs 1kg and is sent flying 3m/s in the Y dimension, the third one is sent flying 10m/s in an unknown dimension. I'm supposed to find the mass of the original rock but i have no idea how i could possibly do this, i've tried using momentum, mass center and kinematic equations but i just can't seem to grasp the answer, I would love if one of you guys could give me a hint <3

>>8545235
The third one must balance out the momentums of the first two.

The first rock travels 1kgm/s in +X, the second rock travels 3kgm/s in +Y.
So the third rock must travel 1kgm/s in -X and 3kgm/s in -Y, and must have such a mass that the associated speed is 10m/s.

((1/m)^2 + (3/m)^2)^0.5 = 10
(1/m)^2 + (3/m)^2 = 100
1/m^2 + 9/m^2 = 100
10/m^2 = 100
m^2 = 10/100 = 1/10
m = 0.316kg

One of my teachers put down 10 as my final grade when I should've gotten a 9 (out of 10)

Should I correct her? Or maybe it doesn't really matter?

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>>8545260
Thank you so much senpai, exactly what i needed. Have a kitten as thanks <3

>>8545269
I'd say you don't have an obligation to correct her, although go ahead and do it if it makes you feel better

>>8544759
Alternatively, where should I ask this?

>>8544759
> How should I use matrices to handle rotation and position of both an object and a viewpoint in three dimensions?
Two 4x4 matrices, one for the model and one for the view. The model's vertices should be transformed by (V^-1).M.

>>8545398
I already implied I had done it before, you've pretty much just told me to do what I've already done.
The fine details are the problem.

>>8545403
What "fine details"?

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How do I do this?

>>8545404
Have you done this without using three.js before?
There's no single way to create a model matrix of a view matrix.

>>8545423
give it your best try first

I've seen derivatives written with uppercase delta, lowercase delta an just the letter 'd'. I'm pretty sure uppercase and 'd' are the same. Is the lower case delta the same?

>>8545423
take div V and use spherical coordinates to integrate

the boundaries should be pretty easy for you to figure out

>>8545423
div has some extra terms in spherical

>>8544159
>>8544230
Thanks

>>8540979

what would it be like if we had a number system like binary but with different place values

maybe the first bit is 1, next bit is worth 2, next bit is worth 3, next bit is worth 4, next bit is worth 5

>>8545721
Derivatives never use delta.

Partial derivatives use a stylised d which looks somewhat like a lower-case delta.

Vector derivative operators (gradient, divergence, curl) use del aka nabla, which looks like an upside-down upper-case delta.

>>8545819
People use some pretty strange bases.

Base factorial comes to mind. There are others I'm sure. You should check them out.

[math]\frac{\sqrt{x}+1}{x\sqrt{x}+x+\sqrt{x}} : \frac{1}{x^2-\sqrt{x}}[/math]
I have to simplify this expression to [math]x - 1[/math], but no matter what I try I can only simplify it to this:
[math]\frac{x^2 - \sqrt{x} + x\sqrt{x} - 1}{x + \sqrt{x} + 1}[/math]
I would write out my whole solving process but it's too much latex.
Can anyone tell me how to do this?

>>8545856
Solved it, nevermind.
Fuck. I hate how I always spend hours with a problem and then when I ask for help I instantly think of a solution.

What jobs can I get with a BSc in Mathematics where someone with a more specialized degree won't be hired over me?

How do I make an "FPS noclip mode" camera in OpenGL

I'm good at openGL logic and memory management, but hopeless at linear algebra

basically what it needs to do is rotate a vector up/down/left/right

and also it needs to translate this vector in local coordinates (it moves the direction it is pointing)

>>8545881
when u ask 4 help, G-d helps u, boder
dog bles

>>8546130
First, you need to maintain the "player" transformation (which will consist of a translation and a rotation about the vertical axis).

Each frame, concatenate incremental transformations for that frame's movement and rotation to the player transformation: P=P.dT.dR.

Then generate the head transformation by concatenating a rotation about the X axis to the player transformation: H=P.rX. The view transformation is the inverse of that: V=H^-1.

/TG/ here what an the formula that produce those numbers at that order?
1, 1.1, 1.28, 1.8, 2.7, 4.5, 9. 27.2

>WTF are those numbers? Why do you need this.

This is related to 3d6
Related to the chance of rolling, 11 compared to rolling 11, 12 compared to rolling 11, 13 compared to rolling 11....
But they are reversed, this means smaller chance means higher numbers

>>8546186
i haven't done the math but it could be a ratio like 1.1 is 10% more likely to roll 12 than to roll 11

>>8546294
or the opposite that 11 is 10% more likely to roll than 12

>>8546186
1,3,6, 10, 15, 21, 25, 27,...

>>8546186
http://stats.stackexchange.com/questions/3614/how-to-easily-determine-the-results-distribution-for-multiple-dice

Hello /sci/ I come bearing a question. Does targeted gene modification in mice/rats carry over to offspring?

For example, opsin gene is inserted into engineered virus, engineered virus containing opsin gene is inserted into brain cells of the host allowing neural activity to be manipulated with light. Somatic cell of host is extracted, the nucleus is removed and placed into enuculeated egg cell, an embryo is formed and placed into a surrogate mother.

Would the offspring have the opsin gene still in the brain?
If so, given how thin and unprotected the skull region of a newborn rodent it, would it be susceptible to death or injury in brightly lit areas?

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Why does statistics have so much notation? What's a good book that will help decode this stuff?

>>8546485
the notation will be explained in any probability/statistics textbook, but at the end of the day a lot of it is just clunky even once you understand it

>>8546161

can you dumb it down a bit

>>8541517
you know difference of 2 squares right?

x - 16 = (x^1/2 + 4) (x^1/2 - 4)

Let's say I have a space X that's path connected. If I cross it with another point from another space, is is still path connected?

That is, suppose X is path connected, y_0 in Y. Is Xx{y_0} path connected?

>>8546618
http://math.stackexchange.com/questions/454627/product-of-path-connected-space-is-path-connected#454631

>>8546587
do you know trigonometry with the unity circle? a point on the unity circle {cos(x), sin(x)} represents a unit vector in some direction. rotate your vertex and then add the unit vector multiplied by how far you want to translate the vertex

>>8546639
*unit circle

>>8546629
I'm not assuming the other space is path connected, is this still fine?

>>8546639

Last few times I tried this I got fucked up on this. I don't get 3d trig.

From what I understand trig doesn't really work well in 3d. lots of tutorials I've seen mention quaternions

>>8546441
>http://stats.stackexchange.com/questions/3614/how-to-easily-determine-the-results-distribution-for-multiple-dice
Thats not what I am asking about, anydice.com already do what the link tell, for me.

What I am asking this
I know the problabylity of rolling 11 on a 3d6 and the probability of rolling 12 on a 3d6 and the probability or rolling 13 on a 3d6......
I want to get those probabilities and find some pattern on it, so I can use on it and find an number for, 19, 20, 21, 22,..... numnbers I cant get on a 3d6

>>8546618
of course. Connect (x1,y0) to (x2,y0) using F(t) = (f(t),y0) where f(t) is the path from x1 to x2.

>>8546655
with euler angles in 3d, the order matters, like it's not just rotating back and forth in one direction, you're twisting etc

rotating in a single plane works the same as 2d but if you have multiple planes you have to do it in the right order

but yeah look into quaternions

>>8546656
http://troubleatthemill.blogspot.com/2013/02/probability-for-wargamers-9-d20-vs-3d6.html
https://en.wikipedia.org/wiki/Normal_distribution

19, 20 etc are literally impossible so you'll have a 0% chance on those

>>8546646
a point is trivially path connected

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How is this not possible?

>>8546688
Normally the chair is feeling a normal force upward from the ground it sits on which allows you to jump upward. However, while you are falling with it, the force you push down onto the chair with will only accelerate it faster while the two of you continue to fall to your impending doom.

>>8546688
I think this might be possible if you push against the chair in an extremely powerful and short impulse right before landing.
if you are 90kg and the chair 10kg, and are falling at terminal velocity of 195km/h or 53m/s you will have 140450 joules of energy.
if you impart that many joules onto the chair it will add an additional 167.6m/s or 603 km/h to its speed and yours should be brought to 0.

show [math]K = X^2 + Y^2 [/math] is a constant of motion for the system of differential equations

[math]x' = 2y - 4(x^2)*y - 4y^3,
y' = -sx +4xy^2 +4x^3[/math]

>>8546886
edit. [math]y' = -2x + 4xy^2 + 4x^3[/math]

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Question for Biofags,

About the the portal vein in humans.

When you shove a suppository up your ass I know it melts and then the substance in it travels through the portal vein to the liver which is then distributed throughout the body.

But wouldn't the substance also directly travel to the small intestine?

If so how much of it would enter the small intestine?

>>8546886
K'=2xx'+2yy' and then plug in the expressions for x' and y'

>>8541577
I had a bout where I tried to do shit without my glasses just to see if I could get by, and if anything would improve (not including driving lmoa).

My eyesight didn't improve and I can tell you that you're better off just wearing them. Anything else is just wishful thinking, and you probably inherited something else positive to balance it out anyway.

>>8546968
seems to be asking to separate x and y method to iterate first

got to [math](y'*y*(2x^2 +2y^2 -1))/(x'*y*(2x^2 +2y^2 +1))=1[/math] and then got lost

K'.. will look into that thx.

How did you decide what to study? What would you suggest to someone who has no real interest in a specific subject, but loves to study (5-8hours a day)?

>>8546886
Try converting x and y to polar coordinates.

Also note the identities for sin(3x) and cos(3x).

yo here's a really stupid question
what the fuck does "t."mean? i see it all the time on posts and i'm not hip and young enough to know

>>8547131
it's like a signature on someone else's behalf

for example, if i wanted to call you a newfag, i would reply to your post with:

t.newfag

>>8541609
LASIK

>>8547131
It means "sincerely" as in "sincerely, Alberto Barbossa"

So when a Portueguese fag says something you cap it with a t. Alberto Barbossa

>>8547135
>>8547149
does it actually stand for anything?

>>8547152
taravastie or something along those lines. finnish
t. mememaster

>>8547152
terveisin, finnish for 'with regards'

>>8541577
>>8541609
you're fucking your shit up

go to a reputable optician and get good glass from hoya or essilor

Find all integer values of [math]x[/math] where the expression [math]\frac{x^2+2x}{x+3}[/math] is a whole number.
I have no idea how to do this.
The answers are: -6, -4, -2, and 0.
Can anyone help me?

>>8547289
note (x^2+2x)/(x+3)=x(x+2)/(x+3).

if x= -2 then (x^2+2x)/(x+3)=0

if x+2 is nonzero then x+2 and x+3 are relatively prime (they differ by one so only 1 divides both of them). so x+3 has to divide x, implying x=a(x+3) for some integer a.

if a is 0 then x=0

otherwise x has to be at most -2, and at least -6 and you can just check these cases by hand

>>8547345
>so x+3 has to divide x, implying x=a(x+3) for some integer a.
I don't understand this part. Why does x have to be divisible by x+3?

>>8547365
if x(x+2)/(x+3) is an integer then x+3 divides x(x+2)

since x+3 and x+2 are coprime x+3 has to divide x

>>8547365
It wouldn't be a whole number otherwise.

>>8547367
Okay, gotcha.
>otherwise x has to be at most -2, and at least -6
And what about this? Where did these numbers come from?

>>8547370
since x+3 divides x you have |x|<=|x+3| which is only possible if x<=-2

if x < -6 then x+3 is more than half of x (look at a number line) and so can't divide x

>>8547371
woops that should say
since x+3 divides x you have |x|>=|x+3| which is only possible if x<=-2

>>8541386
feynmann has a good method

>>8543264
add/subtract the equations from each other

>>8547378
Okay, thank you.

[math](\frac{1}{243})^(\log_9 x) \times\frac{1}{\sqrt2}[/math]
[math]x = (2^\sqrt[4]{27})^\sqrt[4]{3}[/math]
Anyone know how to simplify this? The first fraction is raised to the power of log_9 x in case you don't see it.

>>8547595
243 is 3^5, so (1/243)^log[9](x) = 1/x^(5/2).

And 2^(27^(1/4))^(3^(1/4)) = 2^(27^(1/4)*(3^(1/4)) = 2^(27*3)^(1/4) = 2^3 = 8

So 1/x^(5/2) = 1/((2^3)^(5/2)) = 1/2^(15/2) and 1/x^(5/2)*1/sqrt(2) = 1/2^(16/2) =1/2^8 = 1/256.

>>8547653
>(1/243)^log[9](x) = 1/x^(5/2)
How did you get this?

>>8547665
hint: 9 is 3^2

>>8547673
I don't know how to raise numbers to the logarithmic powers, but I think I somewhat understand how you got that. Thank you.

Scientifically thinking, do black people have the same intellectual capacity as whites or asians?

2 questions:

1) How likely is it that we will encounter intelligent extraterrestrial lifeforms within the next 40-50 years?
2) How likely is it that we will be able to breed with them?

>>8547717
kys, dicklet

>>8547289
write it as x-1+3/(x+3). x is an integer, so this is an integer when x+3 divides 3. But 3 is prime, so x+3 must be -3,-1,1 or 3, so
x must be -6,-4,-2 or 0.

>>8547717
"Scientifically"
>>>/pol/
>>8547790
Mad nigg nogg detected

>>8547732
>How likely is it that we will be able to breed with them?
Dude. Seriously. How much of an idiot are you? How could humans breed with a lifeform fundamentally different in every way, most probably lacking ovules and sperms, perhaps not even being made out of cells and who may not reproduce sexually? You either are a troll or a desperately sexually degenerate guy with sick fantasies.

>>8547817
Isn't it possible that convergent evolution or something could result in a lifeform with similar genetic code to ours even if it evolved completely separately?

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>>8547717
no. it has been shown in various studies and measurements.

imo it's probably correlated with how much neanderthal DNA a person has, but i don't know to which extent it has been proven. east asians and europeans have the most neanderthal DNA whereas africans have little to no neanderthal DNA. it is thought that neanderthals were more "autistic" and less socially cooperative than homo sapiens but not necessarily less intelligent.

WHAT ARE THE BEST BOOKS ON OPTIMIZATION

LINEAR PROGRAMMING
INTEGER LINEAR PROGRAMMING
GRAPHS
P VS NP

I NEED TO KNOW EVERYTHING ABOUT IT IN 6 WEEKS. THE MORE PROOFS AND MATHEMATICAL RIGOUR, THE BETTER.

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>>8548141
that stat includes south asians who are generally 80ish IQ.

explain.

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>>8548309
east asians are ludicrously smart and pull up the average

how many blacks and south asians do you see tinkering with robotics and stuff like this webm in their spare time?

>>8543479
depends what the question means by half of a trip.
could be time, but could also be distance

>>8548373
this

but they probably mean the distance. think of a trip as in a vacation (road trip) and you're stopping for a while in the middle, then you'd be talking about distance rather than time.

>>8548309
south asians who are in the us come through working visas, which only the brightest out of those countries get.
that also explains, why african blacks do way better than african americans in america.

>>8540979
I'm having trouble understanding a part of the Fundamental Theorem of Calculus:

[math] \int_{a}^{x} f(t) dt = g(x) [/math]

Does this mean

[math] \int_{a}^{x} t^2 dt = x^2 [/math]

Or

[math] \int_{a}^{x} t^2 dt = 1/3 x^3 [/math]

>>8548633
I'm not sure what you mean by what you wrote, but here are the two fundamental theorems of calculus:

1) If [math]g'(x) = f(x)[/math] in [math][a,b][/math], then [math]\int_a^b f = g(b) - g(a)[/math].

2) If [math]F(x) = \int_a^x f(t) dt[/math], then [math]F'(x) = f(x)[/math].

>>8548698
Yeah so for 2)
[math] d/dx \int_{a}^{x} f(t)dt = f(x) [/math]
?

>>8548703
yup

>>8548703
>>8548710
For a concrete example, say [math]F(x) = \int_1^x t^2 dt[/math].

By the first fundamental theorem of calculus, you can simplify this to [math]F(x) = x^3/3 - 1/3[/math]. If you take the derivative of this, you'll see it's x^2, which is what's predicted by the second fundamental theorem.

>>8548710
so then otherwise
[math] \int_{a}^{x} t^2 dt [/math]

For example, is
[math] \int x^2 dx = 1/3 x^3 [/math]
?
Or
[math] \int_{a}^{b} x^2 dx = F(b) - F(a) [/math]
?

if y = f(x) is there any difference between df/dx and dy/dx?
I keep getting confused about the notation cos this book switches between them at random

>>8548716
OOH, I see. So it's

[math] \int_{a}^{x} t^2 dt = F(x) - F(a) [/math]
where
[math] F(x) - F(a) [\math]
is actually your function, f(x)... (right?)

>>8548734
I didn't even need TeX for that...

>>8548730
[math] \frac d{dx} [/math] is a derivative operator.
[math] \frac d{dx} f(x) [/math] is taking the derivative of f(x) with respect to x
If y = f(x) then
[math] \frac d{dx} y [/math] is the same thing as [math] \frac dy{dx} [/math]

>>8548749
**same thing as [math] \frac{dy}{dx} [/math]

>>8547106
spot on.

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Can you guys recommend some god tier books / references in the field of electromagnetics and semiconductor physics?

Preferably something with self study problems and solutions. Thanks.

>>8548756
http://4chan-science.wikia.com/wiki/Electrical_and_Electronics_Engineering

>Semiconductor Device Physics
Semiconductor Device Fundamentals by Pierret
Semiconductor Physics And Devices: Basic Principles by Neamen
Device Electronics for Integrated Circuits by Muller and Kamins
Advanced Semiconductor Fundamentals by Pierret
Physics of Semiconductor Devices by Simon M. Sze and Kwok K. Ng

>Electromagnetics and Transmission Lines
Introduction to Electrodynamics by Griffiths (Physics theory)
Electromagnetics with Applications by Kraus and Fleisch
Field and Wave Electromagnetics by Cheng
Fundamentals of Applied Electromagnetics by Ulaby, Michielssen, and Ravaioli
Engineering Electromagnetics by Hayt and Buck (Additional reference)
Electromagnetic Wave Theory by Kong (Advanced)
Advanced Engineering Electromagnetics by Balanis

How do you find the electron-pair geometry and molecular geometry of something like H2C2O4? There's no true "center" to it.

>>8548791
Look at each non-hydrogen atom separately. Each of those atoms has its own geometry that contributes to the overall molecules shape.

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Does the Big Bounce theory hold any credibility or is it just a way for people to make themselves feel good about existential dread?
Pic somewhat related

>>8548848
Can't find the theory, but it lines up with calculations showing that after 10^some large number, years or seconds (doesn't matter), random fluctuations of tunneling particles and anti-particles *could* create a universe out of a false vacuum.

If it didn't have ANY credibility it would be thrown out immediately, but I think you're on the wrong website entirely for a more in depth explanation.

>>8548734
As I defined it, F is a function which takes in a real number x, and returns the area under the curve of f between t = a and t = x. If g is any antiderivative of f, then F(x) = g(x) - g(a) by the first fundamental theorem of calculus.

You sort of seem to be implying F is defined to be the antiderivative, but it's not, it's an area function. Just to try and be totally clear:
1) [math]\int f(t) dt[/math] is the antiderivative of f. More specifically it's a set of functions whose derivative is f. This is why you always need to write [math]\int f(t) dt = blah + c[/math], when you were writing before [math]\int x^2 = x^3/3[/math], that's technically not correct.

2) [math]\int_a^b f(t) dt[/math] is the area under the curve of f between t = a and t = b. In principle, this has nothing to do with the antiderivative, except the fundamental theorems of calculus relate this notion of area to anti-derivatives.

>>8548870
I guess I should have been more succinct.

I know F is an area function under f(t).

>This is why you always need to write ∫f(t)dt=blah+c∫f(t)dt=blah+c, when you were writing before ∫x2=x3/3∫x2=x3/3, that's technically not correct.
I was just choosing the antiderivative where c = 0, for convenience.

Say I want to find the residue of a function f(z) = g(z)/h(z). g(z) is analytic everywhere and doesn't have poles, while h(z) does have poles. Will the residue of 1/h(z) and the residue of g(z)/h(z) be the same? That is, if I'm trying to find the residue of a quotient and the numerator has no poles, should I calculate only the residue of 1/denominator?

>>8545218
>>8545195
>tfw got a 66% on test
>raised my grade from a 72% to a 77%

i have no idea how this grading system works but okay

>>8548889
no. the residue of z2/z at zero is not the same as the residue of 1/z at zero.

But if h has a pole at z0, then 1/h has a zero at z0, not a pole. g/h has poles where g has poles and where h has zeros, unless these cancel out.

>>8548730
this is why we should avoid crappy notation.

if y and f are functions and y=f, then obviously their derivatives are equal.

>>8548904
How about (z^6 + 1)/(z^3)(z - 2)(z - 1/2) ?

I know this function has simple poles at z = 2 and z = -1/2 and a third order pole at z = 0. I've no idea how to calculate the residue of this. Tried using the limit of the derivative rule but it's getting me nowhere. I'd be glad if you could shed some light on this problem.

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How do you do #2? My attempt doesn't work and gets answer choice D

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I don't get this one either. Help?

Any EE's in here that can tell me wheres the best place to start learning some basic engineering? Basic concepts and whatnot?

What exactly is the second moment of an object and how does it relate to the moment of inertia? In a literal sense, what is it?

>>8549270
Well, first calculate the amount of KOH and HCl, which I see you did. We have .006 mol KOH and .010 mol HCl.What you do now is subtract the number of moles of KOH from the number of moles of HCl to get the effect H+ concentration, as the OH ions will neutralize an equivalent number of H+ ions. Now, as you've written on the sheet, the pH is the negative log of the H+ concentration, so simply take the negative log of the [HCl] - [KOH] to get your answer.

>>8549270
Is this A Level shit?

For a given Number [math]c\in\mathbb{C}[/math], we look at the recursive defined, complex sequence with:
[math]z_{n+1}=z_n^2+c[/math]
for [math] n\in\mathbb{N}[/math] and [math]z_0=0[/math]. Draw (for example with the help of a calculator) all [math]c\in\mathbb{C}[/math] for which the sequence [math](|z_n|)_{n\in\mathbb{N}}[/math] stays bounded.
(Note: If you color the resulting picture it will be a pretty motive for christmas cards)

How would i go about this task? perhaps someone can explain how i could get the result of wolfram alpha or something similar for example?

>>8549284

>basic EE concepts

Math and physics.

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Any examples of this?

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>>8549507
Could it be that they just talk about pic related? i don't know of any sensors that would be able to replace a DAC?!

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>>8540979
Could anyone point a poor CS brainlet to any material where this (geometric sum raised to a power) is explained in a little more detail? It only half makes sense to me

No.8548912
> How about (z^6 + 1)/(z^3)(z - 2)(z - 1/2) ?
> I know this function has simple poles at z = 2 and z = -1/2
+1/2, unless you got the sign wrong.
> and a third order pole at z = 0. I've no idea how to calculate the residue of this. Tried using the limit of the derivative rule but it's getting me nowhere.
At c=0, n=3,
(z-c)^n*f(z) = (z^6 + 1)/(z - 2)(z - 1/2)
d^2/dz^2 (z-c)^n*f(z) = (96.z^8 - 600.z^7 + 1272.z^6 - 960.z^5 + 240.z^4 + 48.z^2 - 120.z + 84)/(z - 2)^3(2.z - 1)^3
At z=0, the numerator is 84 and the denominator is (-2)^3*(-1)^3=8, so the residue = 84/8 = 21/2.

Most of the effort is in differentiating (z^6 + 1)/(z - 2)(z - 1/2) twice while retaining the denominator factorisation. Using a CAS is advisable unless you're supposed to do this by hand.

>>8549526
Nevermind, I get it now

>>8543581
>/lgbt/
Found the engineer

can any of you guys explain to me as if i were a retard, the relation between elliptic curves and number theory?

>>8540979
The trace function replaces the sum over the vectors w and w' indexed by k. The diagonal of the matrix stays along A subscript k,k

>>8549548
do you know anything about elliptic curves already/what kind of info are you interested in?

the points of an elliptic curves just have really rich structure which allows for a lot of applications depending on what field you're working over

you can associate a non-negative integer called a 'genus' to nice polynomials in two variables. genus 0 polynomials have infinitely many points, when the genus is at least 2 you always have finitely many points, and elliptic curves are the genus 1 case where things are most interesting because you can have either finitely or infinitely many points

over a finite field you can do cryptography, over the complex numbers an elliptic curve can be thought of as a torus, over the rational numbers you get deep connections to modular forms (complex functions satisfying a nice functional equation) that lets you solve fermat's last theorem

>>8549529
Okay, so I was doing it the right way. Basically, I use the simple pole method to find the residue at z = +1/2 (not worrying about the pole on z = 2 because I'm integrating over the unit circle), that is, taking the limit of (z - 1/2)f(z) as z -> 1/2.

Then, to find the pole at z = 0, I use the method for finding a pole of order 3, that is, (1/2!) times the limit of the d2/dz2[z3f(z)] as z -> 0. Am I correct? I thought I was wrong because the differentiating process seemed to be way too tough, so I was wondering if it was correct.

The original integral was cos(3theta)dtheta/(5 - 4costheta). Then I made z = exp(itheta) and so on and so forth to get that.

>>8549502
Anyone has advice on this? I'd appreciate it greatly.

>>8549568
google image search for 'mandelbrot set'

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Why most images of Cartwheel Galaxy includes two other galaxies on a side? Are they part of Cartwheel Galaxy?

>>8549561
> Then, to find the pole at z = 0, I use the method for finding a pole of order 3, that is, (1/2!) times the limit of the d2/dz2[z3f(z)] as z -> 0. Am I correct?
Yes.
> I thought I was wrong because the differentiating process seemed to be way too tough
I wouldn't do it by hand unless you have to. In which case, I'd start by working out the second derivative of u/(v*w), using the fact that the derivatives of v and w are constants to simplify at each step.

https://www.youtube.com/watch?v=6HCz1tFqIcs

explain what the fuck this is about and whats happening here

>>8549681
what exactly are you confused by? its pretty straightforward

>>8549696
nice try
here extra for you:
>explain with your own words what is happening
jesus...

>>8549706
...do you even know what the words in the video mean?

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>>8549724
do you?
this is a stupid questions thread - not a stupid answers thread

>>8549502
The algebraic approach is to figure out the set of c for which z_n converges to an attractive fixed point (hint: it's the cardioid shape on the right defined by c=(mu/2)(1-mu/2) for |mu|<1), then those for which z_n, then those for which it has attracting cycles of period 2, 3, 4, etc. The cycle of period 2 is the circular blob on the left, other cycles of even period surround this, while other cycles of odd period surround the cardioid. In both cases, the periods increase as you get closer to the point where the cardioid meets the period-2 bulb.

For more information on the structure of the Mandelbrot set, see:
https://en.wikipedia.org/wiki/Mandelbrot_set#Main_cardioid_and_period_bulbs

This allows you to construct a reasonably detailed approximation to the Mandelbrot set "by hand" (i.e. with relatively few calculations compared to brute-force rasterisation).

I'm 19, about to start at a CC. I want to pursue computer science as my major when I transfer to a uni.

I'm garbage at math though (see below). I barely scraped by algebra I and II in highschool.
I'm not one of those people who "hate math". I love math, it's fascinating to me, and I desperately want to become good at it.

Is all hope lost for me? I was wondering if I could possibly use khan academy and diligence to re-teach myself from or if I should just reconcile myself to an IT/IS monkey forever

(Background)
------

The thing is, as a little kid, I was one of the "special" kids, I never had to study anything. Language Arts, Sciences, Social Studies, they all came naturally and I could just do them. All of them besides math.
I figured "why should I study for math when I'm good at everything else? I shouldn't need to study." or something like that. Now I have a shaky-at-best mathematical foundation and I guess I fucked myself over because Math is one of the subjects where you can't just memorize a book and ace the course.

This is all becoming apparent to me, thus leading me to my questions above

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How on earth does this cell work? Why would electrons flow through the wire rather than the electrolyte? Why does changing the cathode material make a difference at all?

>>8549304
That's incorrect. It gives the answer as pH is 2.4, when it's 1.4.

Does anyone know how to solve?

>>8546688
Conservation of momentum and conservation of kinetic energy, you brainlet.

>>8543788
gay

w(t) = w(0)e^kt

k is a constant, t is time.

Why is my prof expressing exponential growth functions like this instead of w(t) = w(0)k^t? What is euler's constant doing in there??????!

>>8549659
Just so close that it's har to crop them out without looking funny

Is a linear manifold essentialy the same as a hull?

>>8549505
I mean like circuitry or whatever you should first know before engineering lab.

>>8549884
In the case of
> w(t) = w(0)k^t
what would be the units of k? t is in seconds, k^t is dimensionless, so k is ...???

Whereas with
> w(t) = w(0)e^kt
k has units of s^-1 (specifically, nepers/sec), while kt, e and e^kt are all dimensionless.

>>8548912
https://en.wikipedia.org/wiki/Residue_(complex_analysis)#Simple_poles

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I don't know if this is the correct place to ask this but since I'm having an anxiety attack I don't care.

Allow me to explain my situation, first half of this year I studied like a madman. I felt like a god on june-july and took my scholarship exams. Out of the 50 applicants I was the only one who passed, got recommended for the MEXT Scholarship (basically free ticket to any uni you want in japan, aiming for todai here, 5 years fully paid).

Now, I got the confirmation and I'm going on april 2017 for the "Preparation year" and having entrance exams on march 2018. (I have to become fluent in japanese by this time since I'm taking it in japanese, but that's not a problem)

The thing is, and the reason for my panic attack, that I feel like a retard right now. Ever since my exams ended I haven't opened a book and spent the whole time partying with friends and distracting myself of everything.

And I would like to issue a request here, if anyone coudl help, I need handholding on how to manage my time (and get a check on my methods and resources)to be able to get a decent level on math and physics for april 2017 (day of my trip). So as not to embarrass myself over there with the other 49 guys from around the world who got awarded the scholarship.
What I wanna do is basically Mechanics, electro for physics. And for math, from pre-calc to math III.
I, NEED, HELP. Fuck I'm sorry

>>8540979
Why the fuck does 1+2+3+4+etc. result in -1/12

Who the fuck came up with such a broken system

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>>8550477
it's a bit sketchy and i don't know what you'd use it for, it's not something you will have to worry about in most everyday situations

>>8550477
https://www.youtube.com/watch?v=sD0NjbwqlYw

>>8550464
>Time management
Can't help you there, because I don't know how much work you can do per day or how much you can actually learn in a day.

http://tutorial.math.lamar.edu/
>Algebra
Preliminaries - Exponent Properties, Rational Exponents, Negative Exponents, Radicals, Polynomials, Factoring, Rational Expressions, Complex Numbers
Solving Equations and Inequalities - Linear Equations, Quadratic Equations, Completing the Square, Quadratic Formula, Applications of Linear and Quadratic Equations, Reducible to Quadratic Form, Equations with Radicals, Linear Inequalities, Polynomial & Rational Inequalities, Absolute Value Equations & Inequalities.
Graphing and Functions - Graphing Lines, Circles, and Piecewise Functions, Function Definition, Function Notation, Function Composition, Inverse Functions.
Common Graphs - Parabolas, Ellipses, Hyperbolas, Absolute Value, Square Root, Constant Function, Rational Functions, Shifts, Reflections, Symmetry.
Polynomial Functions - Dividing Polynomials, Zeroes/Roots of Polynomials, Finding Zeroes of Polynomials, Graphing Polynomials, Partial Fractions.
Exponential and Logarithm Functions - Exponential Functions, Logarithm Functions, Solving Exponential Functions, Solving Logarithm Functions, Applications.
Systems of Equations - Substitution Method, Elimination Method, Augmented Matrix, Nonlinear Systems.

1/? (~3)

>>8550521
>Calculus I
Algebra/Trig Review - Trig Functions and Equations, Exponential Functions and Equations, Logarithm Functions and Equations.
Limits - Concepts, Definition, Computing, One-Sided Limits, Continuity, Limits Involving Infinity, L'Hospitals Rule
Derivatives - Definition, Interpretations, Derivative Formulas, Power Rule, Product Rule, Quotient Rule, Chain Rule, Higher Order Derivatives, Implicit Differentiation, Logarithmic Differentiation, Derivatives of Trig Functions, Exponential Functions, Logarithm Functions, Inverse Trig Functions, and Hyperbolic Trig Functions.
Applications of Derivatives - Related Rates, Critical Points, Minimum and Maximum Values, Increasing/Decreasing Functions, Inflection Points, Concavity, Optimization
Integration - Definition, Indefinite Integrals, Definite Integrals, Substitution Rule, Evaluating Definite Integrals, Fundamental Theorem of Calculus
Applications of Integrals - Average Function Value, Area Between Curves, Solids of Revolution, Work.

2/4

>>8550527
>Calculus II
Integration Techniques - Integration by Parts, Integrals Involving Trig Functions, Trig Substitutions, Integration using Partial Fractions, Integrals Involving Roots, Integrals Involving Quadratics, Integration Strategy, Improper Integrals, Comparison Test for Improper Integrals, and Approximating Definite Integrals.
Applications of Integrals - Arc Length, Surface Area, Center of Mass/Centroid, Hydrostatic Pressure and Force, Probability.
Parametric Equations and Polar Coordinates - Parametric Equations & Curves, Calculus with Parametric Equations (Tangents, Areas, Arc Length and Surface Area), Polar Coordinates, Calculus with Polar Coordinates (Tangents, Areas, Arc Length and Surface Area).
Sequences and Series - Sequences, Series, Convergence/Divergence of Series, Absolute Series, Integral Test, Comparison Test, Limit Comparison Test, Alternating Series Test, Ratio Test, Root Test, Estimating the Value of a Series, Power Series, Taylor Series, Binomial Series
Vectors - Basics, Magnitude, Unit Vector, Arithmetic, Dot Product, Cross Product, Projection
Three Dimensional Coordinate System - Equations of Lines, Equations of Planes, Quadratic Surfaces, Functions of Multiple Variables, Vector Functions, Limits, Derivatives, and Integrals of Vector Functions, Tangent Vectors, Normal Vectors, Binormal Vectors, Curvature, Cylindrical Coordinates, Spherical Coordinates

>>8550529
>Calculus III
Three Dimensional Coordinate System - Equations of Lines, Equations of Planes, Quadratic Surfaces, Functions of Multiple Variables, Vector Functions, Limits, Derivatives, and Integrals of Vector Functions, Tangent Vectors, Normal Vectors, Binormal Vectors, Curvature, Cylindrical Coordinates, Spherical Coordinates
Partial Derivatives - Limits, Partial Derivatives, Higher Order Partial Derivatives, Differentials, Chain Rule, Directional Derivatives, Gradient.
Applications of Partial Derivatives - Tangent Plane, Normal Line, Relative Extrema, Absolute Extrema, Optimization, Lagrange Multipliers.
Multiple Integrals - Iterated Integrals, Double Integrals, Double Integrals in Polar Coordinates, Triple Integrals, Triple Integrals in Cylindrical Coordinates, Triple Integrals in Spherical Coordinates, Change of Variables, Surface Area.
Line Integrals - Vector Fields, Line Integrals With Respect to Arc Length, Line Integrals With Respect to x and y, Line Integrals of Vector Fields, Fundamental Theorem of Line Integrals, Conservative Vector Fields, Potential Functions, Green's Theorem, Curl, Divergence.
Surface Integrals - Parametric Surfaces, Surface Integrals, Surface Integrals of Vector Fields, Stokes' Theorem, Divergence Theorem.

Anything you feel comfortable with skip over, since you only have ~4 months.

>>8550540

>Mechanic
>Electro
To what level? Those tend to be quicker to do and learn since actual physics classes go kinda slow and have a fuck ton of labs. If you just wanna know what to do then

If you have money (Or can find a good Torrent, sorry can't recommend since probably breaks some global rule) then
http://4chan-science.wikia.com/wiki/Physics_Textbook_Recommendations
>Electrodynamics
Griffiths - Introduction to Electrodynamics[Errata 1] (The standard at most universities)
Schwarz - Principles of Electrodynamics (Dover Books on Physics) (A cheap alternative and/or supplement to Griffiths, it's a tad more advanced and mathematical and with an emphasis on SR)

>Classical Mechanics
Taylor - Classical Mechanics <<< Can confirm very good book, that's what I used.

Hi,

I have f(x, n).
Does a positive Hessian Matrix actually says anything about the maximum(s) of the function ? Can it means my function has no maximums ?

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>>8550464
>uni in japan
>Ever since my exams ended I haven't opened a book and spent the whole time partying with friends and distracting myself of everything.

You're already living the Japanese Uni live. No one takes it seriously and parties all the time.

>I have to become fluent in japanese by this time since I'm taking it in japanese, but that's not a problem

You should be panicking on that if anything. How good are you at 漢字?

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>>8540979
If I wash a pic related with sulfuric acid how can I make sure it's safe to drink from again?

Can you recommend a safer alternative to clean it? It's nearly completely clogged

I've tried citric acid which made it look nice and white but it's still clogged and anything put through it tastes like ass now.

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Would an EE shooting for grad school in some applied physics area benefit from going through Jackson's E&M book, assuming he basically has nothing else to do?

Is it just too pure physics oriented and/or theoretical? Would it make sense to go through a more applied approach to E&M?

>>8540979
Someone wanna explain how to use the normal form of a transition matrix to solve differential equations?

Currently working on
[eqn] \ddot{x} + 2 \dot{x} + x = 0 [/eqn]
Letting [math] v := \dot{x} [/math], gives
[eqn]

\begin{pmatrix}
\dot{v}\\
\dot{x}
\end{pmatrix} =
\begin{pmatrix}
-2 &-1\\
1 &0
\end{pmatrix}
\begin{pmatrix}
v\\x
\end{pmatrix}
[/eqn]
Letting the matrix equation be [math] \dot{X} = A X [/math]
The characteristic values are both 1.

And that's about as far as I can get with repeated characteristic values.
How do I find the rotation matrix P such that
[math] P \dot{X} = P A P^{-1} P X [/math]
I know that the normal form of A should be given by
[eqn] J = P A P^{-1} = \begin{pmatrix} 1 & 1\\ 0 & 1 \end{pmatrix} [/eqn]
and that if I find P, I can define U such that [math] U = P X [/math],
and use some easier differential equation solutions to solve the new [math] \dot{U} = J U [/math]

>>8551075
several flushes with water will wash away all the sulfuric acid. Why you want to drink something that's gone through lab equipment is beyond me, though.

>>8551154
Thank you.
I use it for codeine CWE

have you guys ever heard of -5 (negative five) being written as "Opposite of Five"?

>>8551107
How much math do you know and how much E&M have you done?

>>8542394
Not really, most of the first-level ODE class is memorizing solutions to typical ODE's... There are a few points involving series, but not much, seeing as it's mostly a footnote in the course -- at least the one I took. Review your integration, trust me.

What is the difference between the codomain of a function and its range?

>>8551175
nope

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>>8551292
Pulled this image off google, it's probably the best way to try and understand the idea.

The codomain of a function is all the values a function is defined to be _allowed_ to take. The range (also referred to as the image) is the set of all values it actually _does_ take on.

For example, you can define a function f: R -> R, which means that the domain is R and it maps to a codomain R. But if f(x) = x^2, the range of the function is only the non-negative numbers.

>>8551075
By cleaning it with soap.
Really, the only reason that acid is dangerous is the incredibly low PH, but if you wash it out with water and then wash it out with soapy water that's going to be a pretty aggressive way to bring the PH back into a tolerable range.

>>8551292
>>8551352
images are super useful to understand this kind of stuff. i also recommend drawing your own as well

>>8542394

Depends on the school and professor teaching it, ODE classes come in different flavors:

ODEs+series methods
ODEs+numerical methods
ODEs+Laplace method
ODEs+separation of variables method of solving PDEs
ODEs+dynamic systems/chaos
ODEs+proofs

>>8551414
and there's ODEs+matrix algebra, the easiest one.

uno -> dos -> trace

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What are some useful tools or techniques to figure out how matric multiplication will affect vectors?
It's a total pain to calculate one possible vector at a time; can I make some sort of 3D map of vectors, rendered based on how the matrix would affect those vectors?

My problem is that when a vertex of an object passes off-camera, my maths causes that vertex to fuck off some random place which of course makes a total mess of rendering.

>>8549894
that's just looks like 'before' -> 'after'

>>8550458
It's the third-order pole he was asking about.

>>8551424
If you're doing perspective projection, everything goes to shit for w<=0, i.e. when the point is level with or behind the viewpoint. That's why you have to performing clipping before projective division.

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>>8551474
I am doing that.
However, your post confuses me.

How would you write a matrix constructor?
The camera+projection part of mine looks like this, and the projection covers both clipping and perspective.
The thing that moves the camera by z-- is there because otherwise the viewpoint orbits around the camera.

>>8542163
What is a "poset of X"?

if the mu opioid receptorreduces the presynaptic reduction of GABA wouldn't opioids make people more anxious and excitable?
Doesn't GABA prevent neurons from getting too excited?

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Learning for my signal processing exam, I can't really figure out what's happening here in more detail. The term on the right is advantageous because you can then substitute e^(jt)-e(-jt)=2j*sin(t), but how to get there?

>>8551660
I know that this is /sqt/, but if you can't figure out something that trivial you just need to switch to liberal arts. There are no complex identities, just those for +,-,*,/.

>>8551660
multiply the left hand side by -2/-2

Hello everyone.

Is there any way to express the sum : [math]\sum_{i=1}^{n-1} \frac{i}{2^i}[/math], which can also be written as : [math]\sum_{i=1}^{n-1} i (\frac{1}{2})^i[/math]

>>8551889
Nevermind.
https://en.wikipedia.org/wiki/Summation_by_parts

NEW THREAD
>>8551670
>>8551670
>>8551670

>>8551478
it might help if you look at how it works algebraically like how the components are multiplied and summed along the rows/columns

>>8551660
no offense but this should be very easy

flip the sign of what's in the parentheses, flip the sign of j to cancel it out, multiply numerator by 2, multiply denominator by 2