QTDDTOT

File: 140 KB, 834x936, Screen Shot 2015-09-12 at 10.31.49 PM.png [View same] [iqdb] [saucenao] [google]

QTDDTOT Anonymous Sat Sep 12 23:42:35 2015 No.7526620 [Reply] [Original]

Stupid Questions

I just can't wrap my head around the concept of "physical meaning".

Is it the probability of y happening at x time/distance/etc?
Is it just saying out loud "y as happening in x?"

Is it that I'm just an idiot?

Anonymous Sat Sep 12 23:55:36 2015 No.7526641

"Technically, what is going on is that the Earth, Sun and all the planets are orbiting around the center of mass of the solar system," writes Cathy Jordan, a Cornell University Ask an Astronomer contributor. "The center of mass of our solar system very close to the Sun itself, but not exactly at the Sun's center."
http://www.realclearscience.com/blog/2014/08/technically_the_earth_does_not_orbit_the_sun.html

How does the solar system have its own gravity well? Or wtf is going on ther

>>	Anonymous Sun Sep 13 02:18:18 2015 No.7526798 File: 80 KB, 600x600, 603.jpg [View same] [iqdb] [saucenao] [google] bump

>>	Anonymous Sun Sep 13 02:22:02 2015 No.7526800 >>7526620 Mathematical equation: y = x Physical meaning: the distance y that you have travelled north is equal to the distance x you have travelled east

Anonymous Sun Sep 13 02:28:38 2015 No.7526804

>>7526620
Yeah I think you're right. The wavefunction represents probability density, and squared it gives the actual probability. I would argue that the wavefunction carries physical meaning, as it can carry relative phase information that is important for interference. I think what it is trying to say is that physical meaning is values that we can directly measure and observe, while not physical meaning is values that are inferred by the theory.

Anonymous Sun Sep 13 02:48:44 2015 No.7526832

>>7526641
The center of mass of the solar system is pretty self explanatory. It's not a "gravity well", it's just the center of all the masses in the solar system. Gravity is reciprocal. The Earth revolves around the sun because the Sun exerts gravitational force on the Earth, but the Earth also exerts a (smaller) gravitational force on the sun. The end result is that the two actually revolve around their center of mass, and since the sun is much more massive that center is close to the sun.

>>	Anonymous Sun Sep 13 02:59:20 2015 No.7526844 >>7526620 What book are you using? Looks to be better motivated than McQuarrie, I'd like to get myself a copy.

>>	Anonymous Sun Sep 13 03:05:00 2015 No.7526850 >>7526844 that's resnick, i believe.

Anonymous Sun Sep 13 03:10:54 2015 No.7526859

>>7526832
They exert equal gravitational force. Look at the equation, or realize an unequal force pair would violate conservation of energy.The sun just feels the force much less because its much more massive.

>>7526620
The physical meaning is this: probability 1 means something is certain or almost certain. In this case, we expect the electron will certainly be located at any instant somewhere inside the whole space it MAY be located. The square of the wavefunction, because its positive everywhere, has an integral that represents probability of finding the electron within the space you integrate over.

Anonymous Sun Sep 13 03:11:51 2015 No.7526861

The probability function can be evaluated mathamatically AND be observed physically. In this case, you're observing some energy state of some particle. We say it has a "physical meaning" because we can go in and prove the claim experimentally. The Psi function that isn't squared is just a concept that we can understand on a mathamatical level

>>	Anonymous Sun Sep 13 03:14:52 2015 No.7526864 File: 569 KB, 2046x3959, 1415968659993.jpg [View same] [iqdb] [saucenao] [google] >>7526804 >>7526804 >>7526861

>>	Anonymous Sun Sep 13 03:15:56 2015 No.7526866 File: 176 KB, 2853x1692, 1434025892728.png [View same] [iqdb] [saucenao] [google] >>7526864

>>	Anonymous Sun Sep 13 03:22:31 2015 No.7526875 >>7526866 Huh. I actually didn't realize Hermitian implied linear until your image omitted "linear" and i went looking. Thanks bro

>>	Anonymous Sun Sep 13 05:17:42 2015 No.7526995 >>7526620 Physical meaning means a measurable quantity. You can measure mod(phi squared) by running trials. You can't measure phi, but you can use it for calculations

>>	Anonymous Sun Sep 13 05:33:41 2015 No.7527003 >>7526995 >Physical meaning means a measurable quantity. no mate the group velocity of a wave is not physical and can be measured

Anonymous Sun Sep 13 23:16:56 2015 No.7528664

In a 2 gallon still, is it reasonable to assume there would be a difference between alcohol % for the first and last bottle that comes out?
Also, does the process of filtering make any changes to the alcohol percentage? or do the alcohol and non-alcoholic portions of the drink both have the same absorbency into the filter?

Bonus question, how does the calorie content of a drink change as the yeast converts sugar into alcohol?

>>	Anonymous Sun Sep 13 23:18:17 2015 No.7528669 File: 9 KB, 149x79, inequalityMedium - Copy.jpg [View same] [iqdb] [saucenao] [google] >>7526620 How do I do this?

Anonymous Sun Sep 13 23:28:05 2015 No.7528696

>>7528669
>ss of the solar system," writes Cathy Jordan, a Cornell University Ask an Astronomer contributor. "The center of mass of our solar system very close to the Sun itself, but not exactly at the Sun's center."
> http://www.realclearscience.com/blog/2014/08/technically_the_earth_does_not_orbit_the_sun.html
> How does the solar system have its own gravity well? Or wtf is going on ther
>>>
>Anonymous 09/13/15(Sun)02:18:18 No.7526798▶
>File: 603.jpg (80 KB, 600x600)

Multiply both sides by 1-x and use quadratic to get roots.

Anonymous Sun Sep 13 23:33:29 2015 No.7528707

>>7528669
Multiply both sides by (1 - x), then get all of the terms on the left-hand (or right-hand) side. Then factor the quadratic polynomial, and the solution should be obvious from there.

Protip: There are probably going to be infinitely many solutions

>>	Anonymous Sun Sep 13 23:55:16 2015 No.7528742 File: 70 KB, 1958x672, step by step.png [View same] [iqdb] [saucenao] [google] >>7528669 I hope I got it all right. Here you go.

>>	Anonymous Mon Sep 14 00:08:50 2015 No.7528773 >>7528707 How can you multiply by 1-x if you do not know if that term is negative or not? You do not know if you have to flip the sign.

Anonymous Mon Sep 14 00:13:16 2015 No.7528782

"How many milliliters of concentrated nitric acid, 69.0% (w/w) are required to prepare 500mL of a 1% (w/w) nitric acid solution?"

It's stupid because I'm in a quantitative chem lab and they just expect us to know how to do this. No lectures, no notes.

I don't even want just the answer. I'd really appreciate being walked through exactly how to do this.

>>	Anonymous Mon Sep 14 00:38:34 2015 No.7528850 >>7528742 think you simplified incorrectly https://www.symbolab.com/solver/step-by-step/%5Cleft%28x%5E%7B2%7D-4%5Cright%29%2F%5Cleft%281-x%5Cright%29%20%3C%20%3D%204/?origin=button

>>	Anonymous Mon Sep 14 00:47:52 2015 No.7528871 >>7528850 God damn, you're right, I messed that up really bad. I built an intersection table for the solutions instead of a sign table.

>>	Anonymous Mon Sep 14 03:55:14 2015 No.7529087 >>7528742 (x^2 - 4)/(1-x) <= 4 (x^2 - 4) <= (4 - 4x) x^2 <= -4x

Anonymous Mon Sep 14 04:28:33 2015 No.7529123
File: 68 KB, 787x546, induction.png [View same] [iqdb] [saucenao] [google]

Question about this solution for a mathematical induction.

How does my professor get from the yellow highlighted region to the red highlighted one?

What sort of maths am i missing which i must understand before i can undertake questions like this?

i don't have a mathematical background,
thanks /sci/

>>	Anonymous Mon Sep 14 04:45:33 2015 No.7529128 >>7529123 He just factored out (k+1)/6. Multiply it out to go back from red to yellow.

Anonymous Mon Sep 14 07:19:55 2015 No.7529224

If we have:

\lim_{x\to a} f(x) = L[/spoiler] and \lim_{x\to b} g(x) = a[/spoiler]

does this imply

\lim_{x\to b} f(g(x)) = L[/spoiler]?

It seems like it should, but for some reason, I can't find any formal proof of this. Can anyone point me in the right direction?

>>	Anonymous Mon Sep 14 07:26:10 2015 No.7529230 >>7526832 Actually the earth exerts the same amount of force on the sun.

>>	Anonymous Mon Sep 14 07:27:25 2015 No.7529231 If the universe is finite, what is at the border that separates the universe from nothingness? Like say you're in a spaceship that can travel faster than the universe can expand and you hit the farthest point of the universe, what happens to the ship?

Anonymous Mon Sep 14 07:38:29 2015 No.7529236 [DELETED]

>>7529224
Actually, I think this fails. If we have:

f(x) = \begin{cases}
0 & x\not= a \\
1 & x = a
\end{cases}
[/spoiler]
and
g(x) = a[/spoiler]

Then /lim_{x \to b} f(g(x)) = 1[/spoiler], but lim_{x \to a} f(x) = 0[/spoiler].

Perhaps it works if f is continuous at a...

Anonymous Mon Sep 14 07:43:07 2015 No.7529242

>>7529224
Actually, I think it fails. If we have:
f(x) = 0, x \not= a[/spoiler] and f(x) = 1, x = a[/spoiler]
and
g(x) = a[/spoiler]

Then \lim_{x \to b} f(g(x)) = 1[/spoiler] but \lim_{x \to a} f(x) = 0[/spoiler].

Perhaps it works if f is continuous at at...

>>	Anonymous Mon Sep 14 07:55:39 2015 No.7529252 is there any system where it's meaningful to have vectors with infinite coefficients?

>>	Anonymous Mon Sep 14 08:01:25 2015 No.7529260 File: 23 KB, 230x81, Capture.png [View same] [iqdb] [saucenao] [google] Does this equation really have no solution? It's from a test but I highly doubt they would throw an unsolvable equation. I got rang(A) = 2 and rang(A*) = 3. Did I do it right?

>>	Anonymous Mon Sep 14 08:03:47 2015 No.7529263 >>7529260 Three equations, 4 unknowns. Can't be solved directly, though you should be able to find x, y, and z in terms of t.

>>	Anonymous Mon Sep 14 08:04:46 2015 No.7529266 >>7529252 Yes, for example sequences are vectors with infinite coefficients.

>>	Anonymous Mon Sep 14 08:06:52 2015 No.7529272 >>7529260 Ignore the first equation and it becomes obvious.

>>	Anonymous Mon Sep 14 08:17:01 2015 No.7529287 What happened to the guy who theorised a cure for cancer with the illegal fitness supplement or whatever?

>>	Anonymous Mon Sep 14 08:29:35 2015 No.7529296 >>7527003 The group velocity most certainly is physical.

>>	Anonymous Mon Sep 14 08:36:20 2015 No.7529300 >>7529231 If you're a 2d creature existing on the surface of a sphere, then your "universe" is finite but there is no "border" between your 2d world and nothingness. Imagine that but with another dimension. Drugs might help.

>>	Anonymous Mon Sep 14 08:43:19 2015 No.7529302 >>7529272 >>7529263 So there are no solutions, is that it? Btw, assuming that the ranks of both matrices A and A* were equal, how would I proceed? Cramer's wouldn't work under these circumstances (3 by 4 matrix).

>>	Anonymous Mon Sep 14 08:43:46 2015 No.7529305 >>7529260 Use the GauB method of solving parameter dependent linear systems As you can see, it has no solution. 0=/=3

Anonymous Mon Sep 14 08:45:40 2015 No.7529308

>>7529302
There is no solutions because of two contradicting equations. If the setup were different, you would be able to solve for x, y, and z in terms of t.

You could proceed in any cause by using standard operations to bring the matrix to RREF. When you do this with this system, you derive a contradiction.

>>	Anonymous Mon Sep 14 12:27:35 2015 No.7529536 File: 49 KB, 736x870, how.jpg [View same] [iqdb] [saucenao] [google] >>7526620 So after fiddling around with some things, I got to this problem. I tried almost everything. Even wolfram alpha couldn't help me with this. So how do I do this exact?

Anonymous Mon Sep 14 12:45:10 2015 No.7529552

I'm a dumb shit trying to remind myself of matrices (I've not touched them in over a year... I can't even remember how to invert a 3*3 matrix by hand any more).

In general, you can't multiply a a*b matrix by a c*d matrix if b is not equal to d. Why then, do I seem perfectly capable of multiplying a 1*1 matrix by a 1*n matrix? Or indeed, any matrix? Or is a 1*1 matrix, by definition, a scalar?

>>	Anonymous Mon Sep 14 12:49:23 2015 No.7529558 >>7529536 Hmm, a worthy challenge anon. It'd help if you worked out all of the x-intercepts and where all of the curves meet and then it'll just be a matter of integration and subtraction, I'm working on it now, but it'll take a while.

Anonymous Mon Sep 14 12:51:34 2015 No.7529563

>>7528782
1% of 500mL is 5mL
so you need 5mL of pure nitric acid
your given solution consists of 69% pure nitric acid
so for every 1mL of solution you end up with 0,69mL of pure acid

the rest is simple arithmetic
to obtain 5mL of pure acid you divide 5mL by 0,69mL
5/0,69=7,246

and that's it
in that 7,25mL of solution you have 5mL of pure nitric acid
fill it up with water until you reach 500mL, and you end up with a concentration of 5mL of acid per 500mL, which is 1%

>It's stupid because I'm in a quantitative chem lab and they just expect us to know how to do this
how did you get in there in the first place, because this is basic chemistry right here
you need to step up your game if you want to get anything done dude

>>	Anonymous Mon Sep 14 12:59:11 2015 No.7529580 File: 36 KB, 650x208, wtf is going on.png [View same] [iqdb] [saucenao] [google] Anyone know what a diagram of this is supposed to look like?

Anonymous Mon Sep 14 13:04:01 2015 No.7529592

>>7529536
>>7529558
>Hmm, a worthy challenge anon. It'd help if you worked out all of the x-intercepts and where all of the curves meet and then it'll just be a matter of integration and subtraction, I'm working on it now, but it'll take a while.

Ok fuck, I've got no clue how to find exactly where those curves meet... time to look for another solution.

>>	Anonymous Mon Sep 14 13:06:34 2015 No.7529594 File: 73 KB, 736x870, best I've got.jpg [View same] [iqdb] [saucenao] [google] >>7529592

>>	Anonymous Mon Sep 14 13:08:39 2015 No.7529600 >>7529536 Try to set it up as an integral it may help you out a bit

>>	Anonymous Mon Sep 14 13:10:03 2015 No.7529601 Is computer systems engineer similar to software engineer?

>>	Anonymous Mon Sep 14 13:12:13 2015 No.7529604 >>7529594 Fuck, my mistake... where I've got 1, it should be 1/a.

>>	Anonymous Mon Sep 14 13:13:31 2015 No.7529607 Is business the best minor for an engineering degree?

>>	Anonymous Mon Sep 14 13:15:49 2015 No.7529610 >>7529594 >>7529536 Idea, if A=0.5B, then A+B=1.5B. B is equal to the integral of where x ln (ax) -x=ln ax to where 1/x=x ln (ax) -x of ln (ax). That might be useful.

Anonymous Mon Sep 14 13:21:06 2015 No.7529620

>>7529558
>>7529592
Well, I've found that the solution to (first time trying latex by the way)
\frac{1}{x} = ln\left ( ax \right )[/spoiler]
is
x = \frac{1}{w\left ( a \right )}[/spoiler]
in which w(a) is the Lambert w function.
The positive solution is
x = \sqrt{\frac{2}{w\left ( \frac{2a^{2}}{e^{2}} \right )}}[/spoiler]
I just can't figure out the solutions to xln(ax)-x=ln(ax)

>>	Anonymous Mon Sep 14 13:21:53 2015 No.7529623 >>7529620 >I just can't figure out the solutions to xln(ax)-x=ln(ax) Same here.

>>	Anonymous Mon Sep 14 13:24:19 2015 No.7529628 >>7529620 >I just can't figure out the solutions to xln(ax)-x=ln(ax) ...Wolfram tells me its only solvable for a=0

>>	Anonymous Mon Sep 14 13:31:39 2015 No.7529637 File: 254 KB, 1600x1200, no useless other-language text.jpg [View same] [iqdb] [saucenao] [google] >>7529620 Here's a visual picture of what I have thus far, because it's a little bit easier on the eye than the latex.

>>	Anonymous Mon Sep 14 14:02:05 2015 No.7529670 >>7526620 Why is the inverse of a 2*2 matrix: (a b c d) Defined as (d -b -c a) When (-d b c -a) Works just as well?

>>	Anonymous Mon Sep 14 14:15:32 2015 No.7529688 >>7529628 Yeah, that's what I found out too. However, using geogebra I found that there is, in fact, a solution which approximates to <span class="math">a\approx 1,39095[/spoiler], also meaning that x probably isn't an integer.

>>	Anonymous Mon Sep 14 16:52:18 2015 No.7529960 File: 35 KB, 680x447, spring_rod.png [View same] [iqdb] [saucenao] [google] Having trouble with this problem. Is the equation not 0.27 = PL/AreaE + P/k? Looking for k here. Not getting the answer I'm looking for.

Anonymous Mon Sep 14 17:00:13 2015 No.7529969

Doing intro to physics here

An elevator is moving downward when suddenly someone presses the emergency stop button. The elevator then comes to rest a short time later. What are the signs for the velocity and the acceleration of the elevator after the button has been pressed but before the elevator has stopped.
I understand that the velocity is negative yet how is the acceleration positive? Wouldn't the fact that the velocity is negative mean the acceleration is also negative?

>>	Anonymous Mon Sep 14 17:28:15 2015 No.7530019 Quick basic algebra question: How does (3x-5)/(3x) simplify? Don't you cancel out the 3x's or something?

>>	Anonymous Mon Sep 14 17:37:24 2015 No.7530038 >>7530019 1 - 5/(3x) is the best you can do. Either divide every term on the top by 3x to get it or see that 3x-5 / 3x = 3x/3x - 5/3x = 1- 5/3x (I've basically said the same thing twice).

>>	Anonymous Mon Sep 14 17:38:16 2015 No.7530042 >>7530038 So you can't simplify it any further, only change the form.

>>	Anonymous Mon Sep 14 19:01:50 2015 No.7530186 >>7529670 you forgot to divide by the determinant of the matrix you want to invert. also the multiplying with the second matrix would not lead to the identity matrix, but minus the identity matrix

>>	Anonymous Mon Sep 14 19:06:06 2015 No.7530197 >>7529670 Because the inverse of a 2*2 is not defined that way. If you multiply that with the original matrix you're not going to get a unit matrix out of it.

>>	Anonymous Mon Sep 14 19:08:05 2015 No.7530203 >>7529087 Be careful. If (1-x)<0 then the sign reverses when you multiply through. Op should note the numerator factors as (x-2)(x+2), giving critical values at x=2,-2 and 1. The expression can only change sign at these points.

Anonymous Mon Sep 14 20:13:57 2015 No.7530301

So working on Mathematica question. Say I have a parametric equation, and I wanted to find a specific distance on the arc length. ((Ie one unit from the start and end) how would I go about this mathematically? Seems like it isn't possible to use arc length formula, but maybe I'm wrong.

>>	Anonymous Mon Sep 14 21:24:50 2015 No.7530361 >>7526620 What kind of job do most people get with a Math major and CS minor? Is data analyst out of the question?

Anonymous Mon Sep 14 21:58:30 2015 No.7530403

You know the uniqueness theorem for differential equations? Does that also apply for partial differential equations?

So, if I get to the end of a problem and my equation satisfies the initial conditions and original differential equation, is it guaranteed to be correct? I don't see any reason why it wouldn't, but I also never saw the proof for the theorem and crazier things have happened

>>	Anonymous Mon Sep 14 22:00:57 2015 No.7530408 >>7530403 Specifically, I'm working on babby's first PDE's, first order separable

Anonymous Mon Sep 14 22:40:59 2015 No.7530464
File: 32 KB, 633x304, forces.png [View same] [iqdb] [saucenao] [google]

Where am I going wrong with this problem? Using the equation P*L/A*E

(30)(400)/(100)(10^2 - 8^2)(pi/4) + (-10)(600)/(100)(10^2)(pi/4)

Is my statics wrong? Not getting the answer I'm looking for.

>>	Anonymous Mon Sep 14 23:07:09 2015 No.7530496 >>7529969 velocity is positive m8. it's changing negatively, which means accel. is negative, but it's still moving at a speed greater than 0mph until stopping.

>>	Anonymous Mon Sep 14 23:17:20 2015 No.7530511 File: 61 KB, 1091x545, the future of education.jpg [View same] [iqdb] [saucenao] [google] >>7530464 >Mastering Engineering ayyyy

>>	Anonymous Mon Sep 14 23:55:25 2015 No.7530572 Can an object be in more than one place at the same time? If the probability of an object being in a chunk of space is certain, does the object exist? The wave function is the spacial frequency. Think about what that would mean physically.

>>	OHP Tue Sep 15 00:10:33 2015 No.7530606 >>7526800 y=x is the most general case for an equation. Isn't it beautiful?

>>	Anonymous Tue Sep 15 00:16:17 2015 No.7530613 >>7530403 There are uniqueness theorems, but they can require other conditions, like bounds on initial conditions. I wouldn't worry about it at this point.

>>	Anonymous Tue Sep 15 00:16:39 2015 No.7530614 >>7530511 isn't this freshman/sophomore level

>>	Anonymous Tue Sep 15 00:18:28 2015 No.7530615 >>7530614 junior level fluids class

>>	Anonymous Tue Sep 15 03:17:03 2015 No.7530773 cnc machining. if I start now, in 2 years will there be jobs or will it be automated?

Anonymous Tue Sep 15 03:21:58 2015 No.7530776

>>7529969
acceleration is a force that is a measurable straight line away from whatever is pushing it away. the elevator had to endure an acceleration to counteract the motion downward it had already been in: up. the other acceleration was the pull of the earth, in the opposite direction. the acceleration of the brakes exceeded that of the earth's attraction.

>>7530496
wtf are you smoking man, give me some

>>	Anonymous Tue Sep 15 12:25:28 2015 No.7531298 File: 3 KB, 268x27, kyjvgrvtkf.png [View same] [iqdb] [saucenao] [google] so, i know the fancy Q stands for the set of rational numbers, but what the hell does Q squared mean here?

>>	Anonymous Tue Sep 15 12:28:33 2015 No.7531302 >>7531298 btw, is there a proper name for those "fancy" letters

>>	Anonymous Tue Sep 15 12:33:09 2015 No.7531308 File: 22 KB, 400x200, such that [math book].png [View same] [iqdb] [saucenao] [google] >>7531302

>>	Anonymous Tue Sep 15 12:37:00 2015 No.7531317 >>7530464 >(10^2 - 8^2)(pi/4) if the wall thickness of a tube is 2mm and its outer diameter is 10mm, then its inner diameter is definitely not 8mm

>>	Anonymous Tue Sep 15 12:37:34 2015 No.7531320 >>7531308 thanks anon, but by fancy letters i meant the fancy Q you use for the set of rational numbers, fancy N, fancy Z etc.

Anonymous Tue Sep 15 12:37:52 2015 No.7531321

How does a recessive gene that doesn't give any advantage in survival become common in a population?

For example, I read somewhere that the gene for blue eyes started with one guy living near the black sea. But how did this recessive gene become so common, considering it doesn't do shit for you regarding survival.

Anonymous Tue Sep 15 12:38:53 2015 No.7531322 [DELETED]

>>7531302
Just the letters themselves (like \mathbb{R}[/spoiler] are in a font called "Blackboard Bold". You can do it in latex with the command \mathbb{R}, replacing R with whatever letter is needed.

\mathbb{Q}^2[/spoiler] refers to the Cartesian product of \mathbb{Q}\cross\mathbb{Q}[/spoiler]. Google that if you don't know what it means, it's fairly simple.

Anonymous Tue Sep 15 12:41:02 2015 No.7531325

>>7531298
Just the letters themselves (like \mathbb{R}[/spoiler] are in a font called "Blackboard Bold". You can do it in latex with the command \mathbb{R}, replacing R with whatever letter is needed.

\mathbb{Q}^2[/spoiler] refers to the Cartesian product of \mathbb{Q} \times \mathbb{Q}[/spoiler]. Google that if you don't know what it means, it's fairly simple.

>>	Anonymous Tue Sep 15 12:46:58 2015 No.7531335 >>7531325 alright, thanks. so if i read this (>>7531298) correctly, the first part reads "for any couple (x,y), where x and y are both part of \mathbb{Q}" ? >babby's first logic

>>	Anonymous Tue Sep 15 18:29:32 2015 No.7531784 >>7530606 You're talking out your arse mate.

>>	Anonymous Tue Sep 15 18:40:47 2015 No.7531811 >>7529688 m8, you find x (for which there will be 2 solutions) for some given a. To say some value of a represents a solution means nothing.

>>	Anonymous Tue Sep 15 19:11:52 2015 No.7531864 >>7531335 Correct.

>>	Anonymous Tue Sep 15 20:02:05 2015 No.7531935 >>7529536 Is this a problem you set yourself? I don't want to devote any more time to it unless I'm sure there is a solution. For now, I think the insight must lie in the fact that the 3 functions are related by their derivatives.

>>	Anonymous Tue Sep 15 20:49:00 2015 No.7532005 >>7531811 >"Find the exact value of a for which: A=1/2*B"

>>	Anonymous Tue Sep 15 21:48:17 2015 No.7532083 File: 2 KB, 125x125, 1430149202163.jpg [View same] [iqdb] [saucenao] [google] >>7529296 the phase velocity I meant

>>	Anonymous Tue Sep 15 23:49:56 2015 No.7532260 i dont understand this equation https://en.wikipedia.org/wiki/Thermionic_emission#Schottky_emission when i solve for delta W at 1,000,000 volts per meter i get a positive work function what am i doing wrong/am i correct

>>	Anonymous Tue Sep 15 23:58:10 2015 No.7532267 >physical meaning >the probability author is retarded, as is everyone defending his claim of "physical meaning"

Anonymous Wed Sep 16 00:20:00 2015 No.7532286
File: 22 KB, 345x125, Untitled.png [View same] [iqdb] [saucenao] [google]

>be me
>try to do homework
>spend 2.5 hours on #13
>unable to do it

I couldn't even do the previous problems either. Is there a way to approach these type of word problems? I've always struggled with word problems. I just do not know how to set it up. If one were to give me the equation and told me to solve, it would be easy, but this is fucking hard. How do I get good with word problems?

>>	Anonymous Wed Sep 16 02:24:57 2015 No.7532476 File: 13 KB, 240x196, 1441250497542.jpg [View same] [iqdb] [saucenao] [google] >>7526866 disgusting

>>	Anonymous Wed Sep 16 03:16:57 2015 No.7532512 >>7532260 i probably should have mentioned that the answer i got was ~10^680,000,000 amps/meter^2 that being because e was raised to the power of a very large number instead of a small negative number

Anonymous Wed Sep 16 05:15:46 2015 No.7532622

>>7532286
>If one were to give me the equation and told me to solve, it would be easy, but this is fucking hard. How do I get good with word problems?
part of problem solving skills is being able to set up equations based on the constraints you're given

is this within a math or thermodynamics class?

Anonymous Wed Sep 16 05:33:05 2015 No.7532647

>>7532005
You were responding to
>I just can't figure out the solutions to xln(ax)-x=ln(ax)
where the goal is to find the roots, x, for some given a.

If you were actually trying to solve
>"Find the exact value of a for which: A=1/2*B"
as you claim, why would you say
>x probably isn't an integer

>>	Anonymous Wed Sep 16 05:59:31 2015 No.7532685 >>7532286 T(t)=T.ambient +(T(0)-T.ambient)*e^(-Kt) Find constant K with 1.5 min, 50 F plug in 15 at temp, find t

Anonymous Wed Sep 16 09:20:51 2015 No.7532858

>>7529536
I finished this... numerically.

Exact solution eluded me, but I narrowed it down to a = 1.3909(4626)

Not certain about the last few decimal places

Not sure what exact solution that refers to, but something involving Lambert W function maybe

Anonymous Wed Sep 16 09:49:10 2015 No.7532894

Not a math question, but i would appreciate an answer from a chemis or chemE.

I'm applying to phd programs for chem and masters programs for chemE this semester. I'm a chem undergrad and i hear the job market in chem has gone to hell. is ChemE fun? i enjoy math and did well in my physics courses. what jobs does a chemE hold other than process engineer? would it be too difficult for me to transfer into a chemE masters program and maintain a B or higher in my engineering courses?

>>	Anonymous Wed Sep 16 10:11:07 2015 No.7532905 Is fish meat? Can /sci/ help me craft a well thought, good argument for why fish and meat are two different things?

Anonymous Wed Sep 16 10:14:56 2015 No.7532911

>>7526620
You project the wave function (which represents all the knowledge about a given system) on a state.

The modulo square of the wavefunction projected onto a state yields the probability of the wavefunction to be in that state. Make sure you understand this point, it's central to QM.

>>	Anonymous Wed Sep 16 10:17:39 2015 No.7532919 >>7531298 For all vectors (x,y) belonging to the rationnals, if x<y, there exists a z belonging to the rationnals such that z is between x and y.

>>	Anonymous Wed Sep 16 12:00:25 2015 No.7533055 The difference in binding energy per nucleon for the isobar nuclides sodium-23 and magnesium-23 is equal to 0.233 MeV per nucleon. What causes this difference?

>>	Anonymous Wed Sep 16 12:00:50 2015 No.7533057 >>7532905 Fish counts as plants culinarily.

>>	Anonymous Wed Sep 16 12:25:20 2015 No.7533091 >>7533055 Come to think of it, it's caused by the differing amount of protons and neutrons, that makes for a deviating mass defect.

>>	Anonymous Wed Sep 16 13:17:22 2015 No.7533139 How should I be thinking about stalks and germs of sheaves? I know OHP can help me.

>>	Anonymous Wed Sep 16 13:57:21 2015 No.7533195 >>7528773 Assume it to be positive, do your stuff, assume it to be negative, do more stuff. If, now, there appears a contradiction in either of the cases, choose the other. That's one day to do them in general.

>>	Anonymous Wed Sep 16 14:55:27 2015 No.7533308 >>7531320 https://en.wikipedia.org/wiki/Blackboard_bold

>>	Anonymous Wed Sep 16 15:21:07 2015 No.7533374 Does real analysis ever become fun? I'm so fucking sick of proving this menial shit in the first few chapters, when does it become interesting?

>>	Anonymous Wed Sep 16 15:41:08 2015 No.7533407 >>7523556 Trying to figure out what this means. For all n in N, there exists an x in X such that gobbledegook ?

>>	Anonymous Wed Sep 16 15:42:20 2015 No.7533410 >>7533407 Fuck, wrong link >>7522829

Anonymous Wed Sep 16 16:12:15 2015 No.7533468

Assume person x is a constructivist and studying topology. Can x then assume two overlapping subspaces to be path connected and conclude from this that their union is also, because any point in their intersection CAN BE joined to any point in either of the sets, or must x construct the actual path? A silly example, but the line between classical and constructivistic mathematics is pretty fuzzy to me.

Anonymous Wed Sep 16 16:15:09 2015 No.7533477
File: 356 KB, 480x626, PacificOcean_amo_2015141_lrg.jpg [View same] [iqdb] [saucenao] [google]

Layman here
What dimensional plane would the universe be considered? If the universe is infinite anywhere you observe in it, then does that mean it has no plane as it is limitless? If it has a boundary, although ever expanding then is it considered a scaling 3D plane?

>>	Anonymous Wed Sep 16 16:18:57 2015 No.7533486 >>7533374 Just skip the exercises that are too easy for you.

>>	Anonymous Wed Sep 16 16:38:59 2015 No.7533513 >>7533374 When you put it down and pick up an algebra book.

Anonymous Wed Sep 16 18:14:26 2015 No.7533731

>>7532260
i figured it out finally after much searching
e in the first part of the equation is 2.718281828 as it should be but e in the second part is the charge of the electron (and they have the nerve to use the same exact symbol) thus compute the lower part for joules then convert to electron volts and you're done

Anonymous Wed Sep 16 18:21:29 2015 No.7533743

Hello /sci/,

Please assist in this statistics and probability question. I am having trouble understanding.

Assume a lottery that offers different tiers of prizes, with the highest tier awarded 10% of the time. Tickets may be purchased in two ways: $1 for one, or a bulk purchase of $10 for 11. Every draw is independent, duplicate prizes may be awarded, and the bulk draw is done all at once.

I wanted to know whether drawing one ticket at a time will save money if you were only interested in winning exactly one prize of the highest tier and then stopping immediately (e.g. imagine drawing the highest tier prize on your first draw - you have saved $9 over purchasing bulk if you stop drawing at that moment) and did the following: 1 - (0.9)^10 = 65%.

If I did this properly, this means that I will win the highest tier prize with less or equal money spent than the bulk purchase about 65% of the time. Question here: am I correct to think that I would only ever lose money compared to bulk if the win occurs on a multiple of 11? Draws number 12, 13, 14, etc would still result in savings if I win, yes?

Final question that I can't wrap my head around, what happens when you are only interested in a couple particular rewards of the highest tier?

Example: you only really want two of the 10 best prizes, so this reduces your idea of winning from 10% to 2%. With this new 2% probability, are you still better off drawing one ticket at a time or purchasing bulk? If you do the above calculation, you get 1 - (0.98)^10 = 18.3%, much less than the 65% above, obviously. I want to know whether bulk has become the superior option at this lower probability, or if purchasing single tickets is still better because of the fact the win can occur earlier in the drawing process.

Thank you.

>>	Anonymous Wed Sep 16 19:24:10 2015 No.7533845 /sci/, I really want a mathematical book that I can read "on the go" rather than some textbook. My highest level completed is Calc 1. What can you recommend me?

>>	Anonymous Wed Sep 16 19:25:09 2015 No.7533849 >>7526620 If we use electrons for electricity,then could we use protons for protricity?

Anonymous Wed Sep 16 19:50:43 2015 No.7533909

In risk, if the attacker throws 3 dice and the defender throws 2 dice then the following probability of outcomes are possible:
Attacker wins: 37.17%
Defender wins: 29.26%
Both lose one: 33.58%

Generally at the end of the games I play, there is usually 1 huge army faces up against the other, with 100s of men. We then multiple the rolls by 5x to make it faster. (Attacker wins, defender loses 10. Defender wins, attacker loses 10. Both lose, both lose 5)
Does doing this affect the overall probability, rather than throwing 5 times?

>>	Anonymous Wed Sep 16 20:00:00 2015 No.7533924 >>7530773 >will it be automated? no

>>	Anonymous Wed Sep 16 20:20:46 2015 No.7533965 If you solved one of the Millennium Problems, would you accept the prize of $1million, especially considering Perelman rejected it?

>>	Anonymous Wed Sep 16 21:18:30 2015 No.7534035 >>7533845 >/sci/, I really want a mathematical book that I can read "on the go" rather than some textbook. My highest level completed is Calc 1. What can you recommend me? Neil Stewart's "From Here to Infinity".

>>	Anonymous Wed Sep 16 21:28:40 2015 No.7534045 >>7533845 anything from Dover press.

Anonymous Wed Sep 16 21:35:27 2015 No.7534054

How badly do I need to be good at Multivariable calculus?

I barely understand whats going in the class, but I can do the stuff. I got an A in my quiz and Im pretty sure I'm gonna get at least a B on my first test. How badly do I need to understand multivariable calculus?

>>	Anonymous Wed Sep 16 21:59:07 2015 No.7534102 I know that gravity affects time, but can time affect gravity?

>>	Anonymous Wed Sep 16 22:01:59 2015 No.7534107 >>7534054 in school? you need it. if you are shit at calc, stuff like dynamics and fluids will rape you.

>>	Anonymous Wed Sep 16 22:06:06 2015 No.7534118 File: 40 KB, 693x136, FUCK0.png [View same] [iqdb] [saucenao] [google] Can someone help me with these? I can't for the life of me figure out how to do the last part of 3 and basically all of 13.

>>	Anonymous Wed Sep 16 22:07:18 2015 No.7534121 File: 272 KB, 409x458, fuck1.png [View same] [iqdb] [saucenao] [google] >>7534118

>>	Anonymous Wed Sep 16 22:08:21 2015 No.7534125 >>7534118 >>7534121

>>	Anonymous Wed Sep 16 22:10:10 2015 No.7534127 File: 152 KB, 497x218, FUCK2.png [View same] [iqdb] [saucenao] [google] >>7534118 >>7534121 and this.

Anonymous Wed Sep 16 22:59:43 2015 No.7534207
File: 977 KB, 1280x720, ro-robot-mr-hack-reveal.png [View same] [iqdb] [saucenao] [google]

When you're dividing by limits, you always look at the highest power of the numerator and denominator and if they are the same, evaluate the equation based on their coefficient, right?

So if we have lim x->infinity of 4x^2 / (3x^2 + 2x + 100), we would get 4/3, right?

However, if it's lim x->infinity of 4x^2 / (3x + 100), then we would get infinity, right?

Conversely, if it's lim x->infinity of 4x / (3x^2 + 100), then we would get 0, right?

Thank you in advance.

>>	Anonymous Wed Sep 16 23:27:42 2015 No.7534248 >>7534207 divide by highest power of 'x', yeah. Watch our for roots though. Realistically if it's indeterminate you want to use L'hop.

Anonymous Thu Sep 17 00:30:10 2015 No.7534381

>>7534107
im pretty good at calc. 1 & 2, but I get lost in the lectures for calc 3 (even though the problems are easier to figure out). I'm relying on memorizing how to solve the problems and I don't bother with the theories or whatever my professor goes. However, If you put a problem infront of me right now that is multivariable calculus, I probably wouldn't be able to do it. I'm in school for Mech.E. So I'm trying to figure out how badly will I need it for my future math and physics classes.

>>	Anonymous Thu Sep 17 01:46:01 2015 No.7534544 >>7528782 >they just expect us to have passed Elementary Chem ... and apparently you didn't.

>>	Anonymous Thu Sep 17 01:55:20 2015 No.7534553 >>7534381 if you need partial differential equations you're fucked

>>	Anonymous Thu Sep 17 01:56:34 2015 No.7534554 >>7533513 yeah, i took abstract algebra before this and it was great

>>	Anonymous Thu Sep 17 10:32:42 2015 No.7534985 >>7534118 >>7534207 You're both doing Stewart's calculus, aren't you?

Anonymous Thu Sep 17 10:57:56 2015 No.7535014

>>7526620
the wave function encapsulates all the physical information about a system, but in order to find out that information you need to do something to that wave function.

and th things you do to it are either apply quantum operators e.g. apply the momentum operator to get the momentum of the system, or you can multiple the wave function by its complex conjugate

>>	Anonymous Thu Sep 17 11:45:49 2015 No.7535060 >>7533743 P-please help.

Anonymous Thu Sep 17 12:14:21 2015 No.7535093
File: 15 KB, 392x360, ojej.gif [View same] [iqdb] [saucenao] [google]

STUPID QUESTION ABOUT BABBY TRIANGLES

In a very elementary treatise on the subject, Sierpinski shows that, given a family of similar Pythagorean triples (right triangles with natural edge lengths), there must exist among such a family a smallest triple whose legs are relatively prime. Say, the similar triples ...(20,48,52), (15,36,39), (10,24,26), ... eventually lead to a "smallest" element, in this case (5,12,13), which means precisely that the legs (5 and 12, here) are relatively prime. This statement of itself is easy to grasp, but its general proof, which Sierpinski immediately gives, has one detail which I'm not getting right away.

He begins with the assumption that the legs x and y of such a triangle (which also has a hypotenuse of z) are NOT relatively prime, which is as good as saying that the present triangle is NOT the "smallest" such in some given family, as described above. From this, Sierpinski derives a smaller triangle. For if x and y are not coprime then there exists a d > 1 which is a factor of both. So we can rewrite x = d x_1 , y = d y_1 , where x_1 and y_1 are just some smaller numbers. In other words, in his argument,

 \displaystyle z^2 = x^2 + y^2 = (dx_{1})^2 + (dy_{1})^2 = d^2 (x_{1}^{2} + y_{1}^{2}) \rightarrow d^2 | z^2 \rightarrow d|z \rightarrow z = dz_{1} [/spoiler]

which eventually "builds" a smaller triangle, which is just all of x_1 - z_1 in the appropriate spots. Which process can continue indefinitely as long as the given x and y are not coprime, and once they are, it stops, hence a smallest triangle exists (and perhaps a procedure for how to get it too).

NOW HERE'S THE BIT I DON'T IMMEDIATELY GET IN THE ABOVE, ALTHOUGH I HAVE A CLUE:

How do we immediately know, as Sierpinski says, that d|z ?

I notice by definition that in "not-smallest" triangles (and the smallest ones too), the sum of the squares of the legs are themselves perfect squares, e.g. 6^2+8^2 = 10^2...

>>	Anonymous Thu Sep 17 12:19:35 2015 No.7535098 >>7534985 Yep.

Anonymous Thu Sep 17 12:39:34 2015 No.7535118
File: 9 KB, 406x345, box_o_help.gif [View same] [iqdb] [saucenao] [google]

>>7529552

I can help with your stupid question, anon! You've phrased matrix multiplication incorrectly, which is why you're confused!

First of all, when denoting the number of rows and columns of a matrix, the convention is to ALWAYS write the number of horizontal rows FIRST, and to ALWAYS write the number of vertical columns SECOND. And so a matrix A with four rows and two columns can be denoted by something like A_{4x2}. But this is arbitrary, and not the important bit.

The important bit is that matrix multiplication is only defined when the number of COLUMNS in the first matrix is equal to the number of ROWS in the second matrix, which is not what you said, assuming you were expressing row-column notation properly! The reason why your latter multiplication works is because (assuming we're saying the same thing), the number of COLUMNS in your FIRST 1x1 <--- [THIS "1"] matrix, is EQUAL to the number or ROWS in your SECOND [THIS "1"] ---> 1xn matrix! Moreover, the matrix you end up with will have the number of ROWS of the FIRST matrix (1), and the number of COLUMNS (n) of the second matrix, producing, by our above convention, a 1xn matrix!

In general, it goes like this. A matrix A_{mxn} and a matrix B_{nxr} , where each index first denotes that matrix's number of rows, followed by the number of its columns, have their matrix product defined in the case where the number of columns in the first matrix is equal to the number of rows in the second matrix. Moreover, this matrix product will have A's number of rows, and B's number of columns (as a mnemonic, I like to imagine that the "inner" indices "vanish", but don't take that literally). So, the matrix product of the above A and B will be some matrix C which can be denoted as follows: C = AB_{mxr}.

The distinction between scalars and 1x1 matrices is mostly academic. matrix multiplication involving a 1x1 matrix is only defined as above, but they "behave" like scalars on row or column matrices, of course.

>>	Anonymous Thu Sep 17 12:49:12 2015 No.7535140 File: 58 KB, 406x345, matrix notation and multiplication.png [View same] [iqdb] [saucenao] [google] >>7535118 I'd just like to add to your comment with pic related.

>>	Anonymous Thu Sep 17 12:51:03 2015 No.7535143 File: 11 KB, 472x468, box_o_help_2.gif [View same] [iqdb] [saucenao] [google] >>7535118 In fact, just to drive this home, the image I randomly picked can be improved like so, to be more obviously in tune with what I've just said:

>>	Anonymous Thu Sep 17 13:05:13 2015 No.7535171 File: 12 KB, 236x231, fucking saved.jpg [View same] [iqdb] [saucenao] [google] >>7535140

>>	Anonymous Thu Sep 17 13:12:43 2015 No.7535189 how would you semplify this >>>/g/50332620 in a single formula? is it even right? I feel like there's a faster method tbh.

Anonymous Thu Sep 17 13:15:35 2015 No.7535197
File: 2.23 MB, 2000x2000, MW.jpg [View same] [iqdb] [saucenao] [google]

Totally stoned guys here (medical reasons), we know that there's a supermassive black hole at the center of the Milky Way. If I understood right: there's a time dilation happening "near" a black hole so is the time experienced "close" the center of galaxy (let's say the Norma arm) the same as Perseus arm for example? Even if it's just a very small difference.

>>	Anonymous Thu Sep 17 13:20:59 2015 No.7535210 >>7535189 >using a formula For fucks sake, just dump that shit in word or something and justify the text.

>>	Anonymous Thu Sep 17 13:27:16 2015 No.7535220 >>7535210 >2015 >he isn't hungry for knowledge it's just for curiosity tbh... oh well, I wasn't even the same anon anyway, I'd just use excel for stuff like this.

Anonymous Thu Sep 17 13:36:43 2015 No.7535237

How can we have operations on sets like union and intersection when there is no algebraic structure (U, \cup)[/spoiler] or (U, \cap)[/spoiler], where S is the set of all sets, since a "set of all sets" would lead to contradiction. I haven't learned that much about them so far so I'm sure there is an explanation.

>>	Anonymous Thu Sep 17 13:37:45 2015 No.7535238 >>7535237 *where U is the set of all sets

Anonymous Thu Sep 17 14:17:18 2015 No.7535321

>>7535237
>>7535238

Beginning in a naive, finite, and narrative fashion, it is conceptually easy (if tedious when working with large finite sets) to take two or more (finite) sets of things, compare them, and determine which things the various sets have in common (intersection), and even to step back and consider what all the things among the sets are that we could ever be concerned with in the first place, and describe larger sets made up of these various finite sets (union). Because these operational notions are of themselves simple (like arithmetic operations), we can begin to describe their opertional properties and make true statements about them in certain cases without need to repair to something as elaborate as "an algebraic structure". The ancients were doing certain algebra, arithmetic and geometry correctly without the benefit of such formalizing concepts, for example. You don't need a calculator or a grounding in xyz modern concepts in order to start doing math... but they can be extremely helpful, once you do have them.

Where paradoxes are concerned, it bears mentioning, especially in the finite cases, that a simple description of what an operation does, is in a sense distinct from "meta" (okay, maybe not that meta) mathematical observations about the larger theory of operations which lead to paradoxes. Russell's paradox, for example isn't (on the surface) anything to do with the very simple and unimpeachable observation that {1,2, Trump} and {Washington, Adams, Trump} have just the one element in common: "Trump".

>>	Anonymous Thu Sep 17 14:52:16 2015 No.7535375 >>7529536 I don't think the exact solutions are needed. The values of the functions at those solutions are known through the equalities. e.g. for f(c) = f'(c) = 1/c F(c) = c*f(c) -c = 1-c It may not be enough but it seems useful.

>>	Anonymous Thu Sep 17 15:14:39 2015 No.7535412 >>7526620 can any goodhearted anon recommend me a good, if not the best, book around about biophysics?

>>	Anonymous Thu Sep 17 15:14:45 2015 No.7535413 >>7526832 >that center is close to the sun. Isn't inside the sun (but off center)?

>>	Anonymous Thu Sep 17 16:06:01 2015 No.7535528 >>7535321 Oh I see, thx.

>>	Anonymous Thu Sep 17 16:08:06 2015 No.7535537 >>7533965 I would. With money like that, I could just say "fuck everything" and devote my life to mathematics.

Anonymous Thu Sep 17 16:44:31 2015 No.7535615

>>7535093

After a bit of thought, I can answer my own question.

In the above, we are forced to entertain the notion of

 \displaystyle z^2 = d^2 (x_{1}^{2} + y_{1}^{2}) \rightarrow z = d \sqrt{ x_{1}^{2} + y_{1}^{2} } [/spoiler]

where z and d were already /necessarily/ natural numbers by assumption (and so, trivially, are their squares). But what of the x_1^2 + y_1^2 term, which I shall simplify hereafter in plaintext as "x+y" (NOT to be confused with the earlier, premised, un-indexed x and y), and especially its square root?

The simple assumption that d and z are integers requires that the radical term is itself also a natural number. For this radical term is nothing other than the square root of a natural number, which natural number "x+y" is either a perfect square (and thus obviously has a natural square root, in which case closure is obviously happy and satisfied) or else NOT a perfect square. And if this natural number is NOT a perfect square, then its square root is necessarily irrational, by a simple, known number theoretic fact about the naturals. And the product of an irrational number √"x+y" and a rational number d is necessarily irrational, but z is rational. therefore we require that √"x+y" is not merely a rational number but inevitably a natural number, and furthermore, that "x+y" is itself a perfect square which just so happens to correspond to our newly described "z", which is just what the Pythagorean theorem prescribes for Pythagorean triples. And from here, we may complete Sierpinski's thought on the matter, eventually dividing through by d^2 to give the smaller Pythagorean triple

 \displaystyle x_{1}^{2} + y_{1}^{2} = z_{1}^{2} [/spoiler]

EXAMPLE: 6^2 + 8^2 = 10^2. gcd(6,8) = 2. 6=2*3, 8=2*4. 2^2 * 3^2 + 2^2 * 4^2 = 2^2 (3^2 + 4^2) = 10^2. 2^2 | 10^2 , 2 | 10. 10 = 2*5, 10^2 = 4 * 25 = 4 (9 + 16), 25 = 9 + 16, 5^2 = 3^2 + 4^2 (with of course gcd(3,4) being 1. :^)

Anonymous Thu Sep 17 17:12:02 2015 No.7535665

>>7534118
Can't read your working, but for 3)

\frac{dP}{dt}=\alpha P[/spoiler]
P=P_0 e^{\alpha t}[/spoiler]

From question:
P_0=500[/spoiler]
P(10)=1.15 P_0[/spoiler]

I will leave you to use this to find \alpha[/spoiler], P(30) and P'(30)

Anonymous Thu Sep 17 17:31:18 2015 No.7535687

>>7534118
For 13)
\frac{dT}{dt}=k(T_A-T)[/spoiler]
i.e. if T is larger than T_A, T decreases

\frac{T_A-T}{T_A-T_0}=e^{-kt}[/spoiler]
\fracT=T_A-(T_A-T_0)e^{-kt}[/spoiler]
\fracT=T_0e^{-kt}+T_A(1-e^{-kt})[/spoiler]

You know T_0=70, T_A=10, T(1.5)=50, so you can find k.

You can now calculate T(1)

You can now set T(t)=15 and rearrange for t.

>>	Anonymous Thu Sep 17 17:33:25 2015 No.7535691 >>7535687 that should read: <span class="math">T=T_0 e^{-kt} + T_A(1-e^{-kt})[/spoiler] also, as a general piece of advice, do not substitute numerical values in until the very end.

>>	Anonymous Thu Sep 17 18:01:25 2015 No.7535729 Will I have to learn many proofs at Uni for Physics? Start in 2 weeks

Anonymous Thu Sep 17 21:40:10 2015 No.7536034

sorry I have like an ultimate dumb like middle school question

10/(10/sqrt(181)) somehow simplifies into sqrt(181)

wolfram alpha says to multiply the numerator by the reciprocal of the denominator, so it would become (10*sqrt(181))/10 and then I can see the 10s simplifying to 1 just leaving sqrt(181)

but why do that? I mean, why multiply the reciprocal of the denominator by the numerator? It seems arbitrary and I don't know why or how it works or why wolframalpha knows it

im not from here I'll promptly fuck off after getting an answer thanks sorry

>>	Anonymous Thu Sep 17 21:43:01 2015 No.7536040 >>7533743 Can someone double check my shitty math and reasoning here? I have a feeling the "freebie" will average out to more wins (or at least a better "expected value") than singles, but need confirmation.

>>	Anonymous Thu Sep 17 21:45:56 2015 No.7536049 >>7536034 Consider this: what is 4/2? what is 4 * (1/2)? Are these equivalent?

>>	Anonymous Thu Sep 17 21:50:13 2015 No.7536059 >>7536034 Let x = 1÷(1÷a). Then multiply by 1÷a, so 1 = x × (1÷a). Then multiply by a, AMD x =a.

>>	Anonymous Thu Sep 17 22:07:18 2015 No.7536090 I'm asked to prove something about { (2^m)(3^m) : m,n in Z} using properties of Z and R. My question is, why R and not Q? Won't the product of (2^m)(3^m) always be rational for integer m and n?

>>	Anonymous Thu Sep 17 22:11:38 2015 No.7536106 >>7533743 If you want at least one highest tier prize then you have to spend ><span class="math">10 on average if you buy singles >~[/spoiler]15.35 on average if you buy in bulk

>>	Anonymous Thu Sep 17 22:19:24 2015 No.7536127 >>7536090 If it was for Q instead of R, it would mislead people to think this has anything to do with specifically rational numbers. I think that's seriously it.

Anonymous Thu Sep 17 22:24:13 2015 No.7536134

>>7526620
I think what's going on is that there is no physical aspect in a wave function, but in a probability density the concept is that you're using the probability as a general likelihood of an event, and thus the concept of a probability density is in essence a full "location" of something that can't technically be quantified that way.

Anonymous Thu Sep 17 22:54:40 2015 No.7536185

>>7526641
There's a law in electricity that says something like "any Gaussian surface around an object of charge absorbs the charge in the same way a point charge would," which basically means any surface of charge behaves like a point charge of some charge. This could sort of apply to gravity, in that since there's only one kind of charge (only positive gravity) it acts around that point of center

Anonymous Fri Sep 18 00:33:32 2015 No.7536343

Hypothetically, if you have a particle with a charge of 9999999 Coulombs, shouldn't the electromagnetic waves produced by this single particle be enough to rip electrons out of their orbitals given any frequency?

also

Let's say you put a metal foil in an electric field with the strength higher than that of the binding energy of every electron in that foil, won't it rip them off of the foil?

>>	Anonymous Fri Sep 18 00:37:05 2015 No.7536348 >>7536343 How would you get a charge that powerful, though?

>>	Anonymous Fri Sep 18 00:38:42 2015 No.7536352 >>7536348 >hypothetically

>>	Anonymous Fri Sep 18 01:10:21 2015 No.7536394 >>7536352 >hypothetically, how would you get a charge that powerful?

>>	Anonymous Fri Sep 18 01:13:31 2015 No.7536398 I was dogshit at anything STEM from 10th grade onwards. Where should I look to in order to start relearning everything?

>>	Anonymous Fri Sep 18 01:14:44 2015 No.7536402 File: 370 KB, 2082x1527, tesla.jpg [View same] [iqdb] [saucenao] [google] What would happen if I waved my hand through a tesla coil?

>>	Anonymous Fri Sep 18 01:15:28 2015 No.7536404 >>7536394 squeeze a bunch of electrons together Now, answer the question

>>	Anonymous Fri Sep 18 01:17:31 2015 No.7536406 >>7536398 There's a lot of OCW courses you could look at. Most of MIT's freshman-required courses have taped versions online. Try there. UC Irvine, UC Berkeley, and Stanford also have courses you could try, if you'd like.

>>	Anonymous Fri Sep 18 01:17:34 2015 No.7536407 >>7536402 I meant to actually say the current, rather than the coil itself. I know what would happen if I clanged my hand into a big piece of metal.

>>	Anonymous Fri Sep 18 01:19:10 2015 No.7536411 >>7536404 10 ^ 27 electrons? Okay. Depends on how far away they are

Anonymous Fri Sep 18 01:20:41 2015 No.7536415

>>7536407
that brings up an interesting point, though: what would happen if you waved your hand and it passed through the metal of a Tesla coil? Would that mean that you became a charged object, or do you bypass the charge as well as the physical matter?

>>	Anonymous Fri Sep 18 01:23:38 2015 No.7536420 >>7536411 Assuming they are [near enough], will it be able to knock off some electrons in some material with ANY frequency?

Anonymous Fri Sep 18 01:26:58 2015 No.7536426

Anyone ever did a titration in a lab where you had to decide your stopping point by the analyte's change in color? I didn't ask my TA but I think the lab manual is really unclear about it.
For example, the stopping point was when the clear solution developed a pink color that lasted over 30 seconds. If the solution is still clear then the titrate hasn't reacted with all of the analyte.

Wouldn't the slightest change in tint indicate that all of the reactants are used up? This should mean a very small amount of pink particles are developing even though it doesn't appear pink, right? I guess they don't want us to think too hard about it...

Anonymous Fri Sep 18 01:34:47 2015 No.7536434

A "crypto" puzzle I can't figure out:
11221221,2122112211,121122212221,_________________________

Obviously they are increasing 2 digits every time, but I can't see the pattern. Anything I find or establish a relationship between 1 and 2, breaks down when I hit the 3rd.

>>	Anonymous Fri Sep 18 01:41:50 2015 No.7536439 >>7536420 technically anything about 1eV is able to knock off some electrons in some material with some frequency. I don't know what that frequency is, but I do know that.

>>	Anonymous Fri Sep 18 01:42:32 2015 No.7536441 Is the intersection of functions always a nonfunction?

>>	Anonymous Fri Sep 18 01:45:03 2015 No.7536446 >>7536439 >some frequency I said ANY, not just one specific frequency

>>	Anonymous Fri Sep 18 03:43:13 2015 No.7536561 Here's a stupid question that I'm having problems with: AB + C = AD + B*C (break out A)

>>	Anonymous Fri Sep 18 03:53:02 2015 No.7536569 >>7536561 AB = AD + BC - C AB - AD = BC - C A(B - D) = BC - C A = (B*C - C) / (B - D)

Anonymous Fri Sep 18 04:08:59 2015 No.7536579 [DELETED]

File: 46 KB, 488x461, wtf.png [View same] [iqdb] [saucenao] [google]

If anyone can help, I got a stupid question. Pic related. In the bracketed red step I can't figure out why he's getting this answer. When I took the partial I got lnx+1-lny, same as the above. Making it exact, but he has a negative lnx? Where is my mistake?

>>	Anonymous Fri Sep 18 04:10:00 2015 No.7536580 >>7536579 Nevermind I answered my own question. It's too fucking late. There's a negative sign in front. Fuck me.

>>	Anonymous Fri Sep 18 04:10:08 2015 No.7536581 >>7536569 thanks! <3 Mind helping me with this one aswell? A^q = B (Break out A)

>>	Anonymous Fri Sep 18 04:13:02 2015 No.7536584 File: 466 KB, 568x499, 1425270957878.png [View same] [iqdb] [saucenao] [google] How do i prove surjectivity of this function?? From Z(interger) to Z f(n)=n-1 and From Z *(cross) Z f(m,n)=2m-n

>>	Anonymous Fri Sep 18 05:07:58 2015 No.7536614 >>7536581 log(A^q) = log(B) qlog(A) = log(B) log(A) = log(B)(1/q) log(A) = log(B^(1/q)) A = B^(1/q)

>>	Anonymous Fri Sep 18 05:16:44 2015 No.7536621 >>7536614 Thank god. Being right occasionaly, even with simple math like this, is what keeps me from killing myself. thx <3

>>	Anonymous Fri Sep 18 06:01:59 2015 No.7536657 >>7526620 The wave function is not an observable, while the square of it is a probability, so it's an observable.

>>	Anonymous Fri Sep 18 06:18:28 2015 No.7536669 Get the area under the curves by integrating, then add/substract areas

>>	H Fri Sep 18 07:35:32 2015 No.7536756 >>7526804 Relative phase is important, but not global phase. The global U(1) symmetry makes the wavefunction unphysical.

>>	Anonymous Fri Sep 18 11:04:55 2015 No.7536996 >>7536581 >(Break out A) Do you seriously mean solve for A?

>>	Anonymous Fri Sep 18 11:15:28 2015 No.7537009 how would you prove this statement? For all real numbers x and all real numbers y, there exists a z such that y*z = x? In other words, that you can multiply any real number by another real number to get any other real number?

>>	Anonymous Fri Sep 18 11:16:29 2015 No.7537010 >>7537009 or is this statement just false and I'm retarded?

>>	Anonymous Fri Sep 18 11:31:09 2015 No.7537027 >>7526620 How can I introduce a new kind of frames in the beamer package of latex? I need to use a different layout on two slides, so I'd like to use something like \begin{frame}[type=xxx].

Anonymous Fri Sep 18 11:44:27 2015 No.7537040

>>7536584
The first one is actually bijective. Just show that there exists an inverse function (the process of discovery is left as an exercise).

The second one is pretty easy. Any integer k can be expressed like k = 2*0 -(-k), giving you a pair (0, -k).

>>	Anonymous Fri Sep 18 12:02:03 2015 No.7537059 >>7536441 If you're defining functions to be sets, then it's just restricting every function to the points where they agree, which should be a function.

Anonymous Fri Sep 18 12:02:07 2015 No.7537060
File: 22 KB, 230x164, maybe.jpg [View same] [iqdb] [saucenao] [google]

So... pic related just trolling right? I can't do double integrals, but almost every terms here seems to cancel and it even looks like they made a mistake on the last line (they've put cosh=).

Is it just the sum of the first 4 terms?

>>	Anonymous Fri Sep 18 12:49:05 2015 No.7537116 can anyone help me with this question: Let A be a set and f,g,h: A -> A be functions such that fog = hof = idA. Show that g=h. I feel like this question is trivial but at the same time can't seem to figure out how to express it

>>	Anonymous Fri Sep 18 12:55:34 2015 No.7537120 >>7537116 g is the inverse of f, f is the inverse of h, inverses are unique

>>	Anonymous Fri Sep 18 12:56:04 2015 No.7537122 >>7537116 I guess what I've figured out so far is that h(g(f(x))) = x (since the function is defined as A --> A) and since h(f(x)) = f(g(x)) = x we have h(g(f(x))) = h(f(x)) =f(g(x)) but I'm not sure where to go from here.

>>	Anonymous Fri Sep 18 12:58:10 2015 No.7537125 >>7537116 for any x in A fog(x)=x h(f(g(x))=g(x) (hof= id) but since fog=x, h(f(g(x))=h(x) since for any x in A h(x)=g(x), h=g

>>	Anonymous Fri Sep 18 13:11:24 2015 No.7537137 Or more simply, for all x in A, h(x) = h(f(g(x))) = g(x)

Anonymous Fri Sep 18 13:45:03 2015 No.7537177
File: 145 KB, 247x455, product-30xiis-feature-image.png [View same] [iqdb] [saucenao] [google]

Should I consider upgrading my calculator? Pic related is my driver normally.

I left it at my place yesterday. So I just borrowed a calculator from the lost and found for an exam, and I was looking over the key and realized that it sorta fugged me over on a few problems. Used to have a TI-83 from my middle school but bit the dust a while ago.

I like this calculator in pic related and it does everything I need at a calc III and phys II level, but formatting can get a little frustrating. I usually just use my phone and have started using Mathematica for more complicated things during homework, but I question my use of a calculator or not until I finish graduating.

TI-84 CE looks neat, but I also wouldn't mind something that is more useful into the future.

>>	Anonymous Fri Sep 18 13:55:07 2015 No.7537193 >>7537177 If you find formatting annoying on TI calculators (and I don't blame you) I suggest you try Casios

>>	Anonymous Fri Sep 18 14:03:07 2015 No.7537211 >>7537177 If you're gonna buy a TI, get a Nspire, but really, calculators are fucking worthless if you're not forced to use them for exams.

Anonymous Fri Sep 18 14:24:59 2015 No.7537233

>>7537193
Lel the one I used was a Casio yesterday that gave me weird Sig figs. But I know a lot of people like them. Any recs for just a daily driver?

>>7537211
Yeah see that's always been my reasoning. I hate people who depend on calculators because a computer does the stuff you can't do better in my opinion and honestly, just git gud.

>>	Anonymous Fri Sep 18 14:30:31 2015 No.7537248 >>7537233 I personnally use a graph35+, cheap and does just about everything I need it to 2nd year in a math/physics combined degree

>>	Anonymous Fri Sep 18 14:51:01 2015 No.7537266 >>7537248 Is it like only available in Europe or something? Can't find it

>>	Anonymous Fri Sep 18 14:56:43 2015 No.7537274 >>7537266 I'm in France, so that might be the case

>>	Anonymous Fri Sep 18 15:07:12 2015 No.7537294 >>7537116 g = idA o g = (h o f) o g = h o (f o g) = h o idA = h

>>	Anonymous Fri Sep 18 15:35:26 2015 No.7537338 Is it bad to be too "verbose" with calculations on a bachelor thesis?

>>	Anonymous Fri Sep 18 15:46:54 2015 No.7537358 >>7537338 Yes. Keep it snappy, but make sure you do know what you're doing.

>>	Anonymous Fri Sep 18 15:57:19 2015 No.7537380 >>7537338 You should be writing enough so that the reader can follow. If you expect the reader can easily verify some simple calculations, then leave them out.

>>	Anonymous Fri Sep 18 16:03:35 2015 No.7537387 Help! In3 + In (x-3)= 0 Is the answer 4/3? For some reason I think k that it is wrong! Basically what I do is In(3x-3) = 0 then I write in exponent form E^0 = 3x -3 1 = 3x - 3 4/3 = x Is this right?

>>	Anonymous Fri Sep 18 16:21:12 2015 No.7537422 >>7537387 ln(x-3)=-ln3 ln(x-3)=ln(1/3) ln is bijective from ]0,+inf[ to R, this gives us (x-3)=1/3 x=10/3

>>	Anonymous Fri Sep 18 16:22:31 2015 No.7537424 >>7537387 ln3 + ln(x-3) = 0 ln (3x-9) = 0 e^0 = 3x-9 x=3 you forgot to multiply the 3 to the other 3 homeboy

>>	Anonymous Fri Sep 18 16:23:31 2015 No.7537428 >>7537424 whoops, i'm retarded. it should be x = 10/3 as anon >>7537422 above said

Anonymous Fri Sep 18 19:26:42 2015 No.7537760

>be in Calculus III at a CC
>professor says that he's being re-assigned
>next day in class a new professor comes in
>check out his ratemyprofessor rating
>1.3

Is it possible to drop the class without ending up with the W? Can I file a grievance or something?

>>	Anonymous Fri Sep 18 22:51:15 2015 No.7538089 is mathematics based entirely around the ZFC axioms

>>	Anonymous Fri Sep 18 23:08:32 2015 No.7538108 >>7529580 this is a rate in-rate out problem from Calc 2 / DE 1, although more complicated with the ratio

>>	Anonymous Fri Sep 18 23:11:24 2015 No.7538112 >>7532286 newton's cooling law

Anonymous Fri Sep 18 23:15:33 2015 No.7538118
File: 26 KB, 500x375, ayy.jpg [View same] [iqdb] [saucenao] [google]

>>7533477
from a layman's POV, planes can also (and usually are) infinite, for example the 3D plane of reals R3 is infinite in all (read: our spatial definition of all as in x y z) directions. for us that could suffice, but from a scientific view we need to consider spacetime as well as time being a 4th dimention. Moreover, we can have infinite dimentions although we might not know even a fraction of what they could look like. I suppose it depends on your POV. for Joe Schmo who works at McDons, the universe could be considered on a 3 dimentional plane. For a quantum physicist, its likely going to be more than that. This is all speculation and logical reasoning on my part, feel free to rip me a new one

>>	Anonymous Fri Sep 18 23:17:57 2015 No.7538120 >>7533845 also consider The Logic Book, not quite a textbook but a great read on formal logic, a huge proponent of upper-maths

>>	Anonymous Fri Sep 18 23:19:01 2015 No.7538124 Is the line integral equal to the square root of the sum of the squares of the integrals of the function's components? answer the fucking question

>>	Anonymous Sat Sep 19 02:23:55 2015 No.7538353 >>7538089 No. There are other axiomatics for set theory than ZF(C), like Bernays-Gödel-von Neumann (with C). Also, even in higher mathematics, many problems can be approached with just the mix naïve set theory and the axiom of choice.

>>	Anonymous Sat Sep 19 02:26:09 2015 No.7538356 >>7538124 >answer the fucking question Ok. I don't know.

>>	Anonymous Sat Sep 19 02:34:46 2015 No.7538364 >>7538124 Give or take a few numbers this is correct

Anonymous Sat Sep 19 03:19:50 2015 No.7538396
File: 204 KB, 786x427, goce_gravity_field_786map.gif [View same] [iqdb] [saucenao] [google]

Because of general relativity the areas with greater gravity would have a slower perception of time right? I get that it would be totally minor and maybe like 1 second different over 50 million years but it would be there right?

>>	Anonymous Sat Sep 19 03:26:53 2015 No.7538404 If I sit 67cm away from my monitor, I'm better off getting a 24" or less monitor than a 27" monitor right? A calculator says 24" @ 67cm distance would be 43.3 degrees viewing angle, which already goes beyond 20/20 central vision.

>>	Anonymous Sat Sep 19 03:58:47 2015 No.7538417 >>7538396 The gravity on Earth is pretty much the same everywhere, so yeah. It's like driving a car 100 km/h makes no notable difference in the perception of time compared to standing still.

Anonymous Sat Sep 19 04:05:52 2015 No.7538423

>>7538417
Yeah but my question is more, is that how relativity works, more gravity or faster movement = slower time perception?

I get that on the scale of earth gravity fluctuations or driving like you say the differences would be unobservable within a lifetime but just in a general sense if we were able to measure to infinite it would change right?

Anonymous Sat Sep 19 04:40:48 2015 No.7538451 [DELETED]

File: 11 KB, 290x228, 111.png [View same] [iqdb] [saucenao] [google]

An air-tight cave has been flooded with water. The difference in height between the two levels of water is equal to 20 metres ([$]x[/$] in the figure).
Show why -- in the part filled with air, designated by an arrow -- the pressure is equal to [$]$2.97 \cdot 10^5 \mathrm{\ Pa}$[/$]

Anonymous Sat Sep 19 04:42:38 2015 No.7538453
File: 11 KB, 290x228, 111.png [View same] [iqdb] [saucenao] [google]

An air-tight cave has been flooded with water. The difference in height between the two levels of water is equal to 20 metres (x[/spoiler] in the figure).
Show why -- in the part filled with air, designated by an arrow -- the pressure is equal to 2.97 \cdot 10^5 \mathrm{\ Pa}[/spoiler]

>>	Anonymous Sat Sep 19 04:44:54 2015 No.7538457 >>7538453 P = P_atm + rho g x Literally babby level shit

Anonymous Sat Sep 19 04:58:48 2015 No.7538469

>>7538457
Thanks for the quick answer.
I thought about using that formula at first, but it didn't make sense to me so I started looking elsewhere. Could you please explain why it works this way? I fail to see why the total fluid pressure is equal to the pressure of the air in the closed end of the cave.

>>	Anonymous Sat Sep 19 05:18:56 2015 No.7538484 >>7538469 If they would not be equal, there would be a net force driving the fluid either up or down. Since this is a steady-state situation the forces must be equal and hence the pressure must be equal.

>>	Anonymous Sat Sep 19 05:26:46 2015 No.7538488 >>7538484 This actually makes a lot of sense. Thank you.

>>	Anonymous Sat Sep 19 05:39:51 2015 No.7538494 File: 95 KB, 600x593, Karl_Popper2.jpg [View same] [iqdb] [saucenao] [google] Do i actually need to read some philosophy of science to study science?

>>	Anonymous Sat Sep 19 06:12:24 2015 No.7538517 >>7538423 Yes. The effect is non-zero, so in an infinite time it would be observable.

Anonymous Sat Sep 19 06:49:50 2015 No.7538529
File: 69 KB, 691x403, Untitled.jpg [View same] [iqdb] [saucenao] [google]

How does this:

\cfrac{1}{4}(k+1)^2+(k+1)^3
[/spoiler]
become this:

\cfrac{1}{4}(k+1)^2[k^2+4(k+1)]
[/spoiler]

see picture for entire context

>>	Anonymous Sat Sep 19 06:50:52 2015 No.7538530 >>7538529 How does this: <span class="math"> \frac{1}{4}(k+1)^2+(k+1)^3 [/spoiler] become this: <span class="math"> \frac{1}{4}(k+1)^2[k^2+4(k+1)] [/spoiler] see picture for entire context

>>	Anonymous Sat Sep 19 07:22:43 2015 No.7538556 >>7538494 No.

>>	Anonymous Sat Sep 19 07:25:46 2015 No.7538559 >>7538556 Similarly, you don't need to study philosophy of plumbing or philosophy of philosophy or philosophy of philosophy of philosophy to study either plumbing, philosophy, or philosophy of philosophy.

Anonymous Sat Sep 19 07:32:03 2015 No.7538564

>>7538530
You forgot a factor k^2 in the first term

 \frac{1}{4} k^2 (k+1)^2 + (k+1)^3[/spoiler]
 =\frac{1}{4} k^2 (k+1)^2 + \frac{4}{4} (k+1)^3[/spoiler]
 =\frac{1}{4} (k+1)^2 (k^2+4(k+1))[/spoiler]

>>	H Sat Sep 19 07:33:34 2015 No.7538565 >>7536434 Read it aloud. One one, two twos, one two, etc.

>>	Anonymous Sat Sep 19 07:43:56 2015 No.7538573 >>7538517 Thanks man. Was wondering if I understood it correctly.

Anonymous Sat Sep 19 07:55:12 2015 No.7538579

I can't wrap my mind around anything smaller than what the human eye can perceive. Microorganisms, blood cells, bacteria, electrons, atoms... When the micro world is spoken of, I can only relate to it as an abstract concept as opposed to seeing it for what it is - something that actually fucking exists. I just can't envision how it fits into the scale of things.

Do you know of a good video you can share (like, a computer-graphics simulation illustrating the sense of scale back and forth between what we can see and below that), or a very clear graphic, or something to help me appreciate how small things fit into our picture.

>>	Anonymous Sat Sep 19 08:04:17 2015 No.7538583 >>7538564 thanks anon

>>	Anonymous Sat Sep 19 08:05:18 2015 No.7538585 >>7538579 this ones pretty cool http://htwins.net/scale2/

>>	Anonymous Sat Sep 19 10:35:47 2015 No.7538689 >>7538585 Fuck I never realised bucky balls where that tiny. Those orbitals acting like orbits tho

Anonymous Sat Sep 19 10:40:46 2015 No.7538692

I've got a problem, either my calculator or google is fucking me over.

I'm working out a parabola where y = -x^2 + 10x - 21

I'm trying to find y when x = 5 so I do -5 ^ 2 + 10 * 5 - 21

Google does it as -5 ^ 2 + 10 * 5 - 21 = 4
My calculator does it as (-5) ^ 2 + 10 * 5 - 21 = 54

I take it google's way is the correct way, but how the fuck do I get my calculator to not fuck it up? I've got a sharp EL-531WH

>>	Anonymous Sat Sep 19 11:08:52 2015 No.7538718 How are grad classes graded I'm in a class of brilliant people and if it's graded on a curve I don't want my GPA to be sunk just because I was only slightly intelligent as opposed to extremely intelligent

Anonymous Sat Sep 19 11:17:48 2015 No.7538724

>>7526641
I believe this is talking about the barycenter of the solar system. The barycenter is vector sum of the force of gravity of all the objects (in the solar system, in this case). All objects orbit around it, The mass of the solar system is close to the mass of the sun because, the sun weighs so much that the sum of the other planets and objects in space are almost negotiable when looking at the barycenter.

>>	Anonymous Sat Sep 19 12:10:05 2015 No.7538785 >>7538692 Is the problem written as -x^2 or (-x)^2?

>>	Anonymous Sat Sep 19 12:18:41 2015 No.7538796 >>7538785 -x^2 The problem is my calculator automatically puts brackets around negative numbers so when I put it in it turns into (-x)^2

>>	Anonymous Sat Sep 19 12:25:41 2015 No.7538803 >>7538796 then input it into your calculator as -(5)^2 + 10 * 5 - 21 = 54

>>	Anonymous Sat Sep 19 12:29:31 2015 No.7538807 >>7538803 Cheers bro that fixes it. I was going back and manually deleting the brackets which was super inefficient.

>>	Anonymous Sat Sep 19 12:29:58 2015 No.7538809 File: 39 KB, 581x588, help.png [View same] [iqdb] [saucenao] [google]

Anonymous Sat Sep 19 14:03:04 2015 No.7538941

I have difficulty with some types of ambiguous double negatives and word problems. How do I "reduce a ratio"? Not reduce it to a simple form, but if a ratio, eg, mean respiratory exchange ratio is "reduced" relative to another measurement, what the fucking fuck is that supposed to mean?

Comparatively, how am I to understand this? The ratio became smaller, but it's composed of two values, which changed and how? Is this information somehow implicit and I just don't realize it?

>>	Anonymous Sat Sep 19 14:21:11 2015 No.7538977 File: 926 KB, 865x634, 599684.png [View same] [iqdb] [saucenao] [google] Why does this reflection on the surface of a puddle of coconut oil give off such a strong theme of conformal transformations in the complex plane?

>>	Anonymous Sat Sep 19 14:22:25 2015 No.7538982 File: 322 KB, 663x309, 567783457.png [View same] [iqdb] [saucenao] [google] >>7538977

>>	Anonymous Sat Sep 19 14:25:40 2015 No.7538991 >>7538809 You do realize those pieces don't move like that? And the bishop would capture the queen.

Anonymous Sat Sep 19 14:30:06 2015 No.7538998

>>7538809
Equal material, but black has positional superiority by far.

Best move by white is to start trading in material.

Best move would be to get rid of that worthless pawn position while simultaneously removing a strong black pawn:
E5 X F6

Next keep trading to open up the centre board, this puts black in a weaker position because he has not moved his castle out yet. Because you know also have the king exposed on the diagonals try setting up a discovery attack.

Anonymous Sat Sep 19 14:31:27 2015 No.7539003 [DELETED]

>>7538809
Equal material, but black has positional superiority by far.

Best move by white is to start trading in material.

Best move would be to get rid of that worthless pawn position while simultaneously removing a strong black pawn:
E5 X F6

Next keep trading to open up the centre board and possibly move the queen there, this puts black in a weaker position because he has not moved his castle out yet. Because you now also have the king exposed on the diagonals try setting up a discovery attack.

If black is an even marginally good player he's already won though.

Anonymous Sat Sep 19 14:59:48 2015 No.7539042

>>7529536
You can always split an area bounded by an arbitrary number of curves into a set of areas bounded by two of the curves and two straight lines.

In this case you can split B into an area bounded by f and F up until the intercept between f' and f. Then the rest of B is bounded by f' and F. A can be split up in a similar way. Now you can compute the area of B and A as a sum of two integrals, so in total you'll have to compute four integrals. Although two of those integrals will have the same integrand (f - F).

An import thing to note is that since the limits of integration depend on the points of interception, they will also depend on a, and it's possible that for some set of a's the curves will intercept at wildly different points, or not at all.

But lets assume for the moment the we restrict ourselves to a set of a's that doesn't change the topology of the problem. Then once you have the (somewhat ugly) integrals, it's simply a matter of setting 2A - B = 0, and solving for a. I don't know if there is an exact analytical solution - what with all the logarithms - but this is how I'd solve this problem.

Well, assuming values of a that don't change the topology. Like a = 0.1: http://www.wolframalpha.com/input/?i=plot+1%2Fx+and+ln%280.1x%29+and+xln%280.1x%29-x+from+0+to+2

>>	Anonymous Sat Sep 19 15:38:37 2015 No.7539110 File: 203 KB, 1920x1200, tdie5Mi.jpg [View same] [iqdb] [saucenao] [google] How do I integrate this: Integrate from 0 to 1 ((1-x^2)^r)dx , where r is positive real number.

>>	Anonymous Sat Sep 19 15:54:36 2015 No.7539126 >>7539110 can always check out the power series expansion and integrate a few terms and see what you function's power series you get

Anonymous Sat Sep 19 15:57:34 2015 No.7539134

>>7539042

Actually you might not even be able to find exact expressions for the intercepts. At least I can't think of anything off the top of my head that would let you solve ln(ax) = xln(ax) - x. In which case you have to solve it numerically. Unless there's some super fancy change of variable / frame of reference that will enable you to wrangle something 'nice' out of those logarithms.

>>	Anonymous Sat Sep 19 16:09:16 2015 No.7539152 >>7539110 Trig substitution, then integration by parts r times.

>>	Anonymous Sat Sep 19 21:54:43 2015 No.7539754 What is the smallest amount of atoms it would take to change a surface enough to be noticeable to the naked eye.

>>	Anonymous Sat Sep 19 21:58:50 2015 No.7539759 >>7534985 Fuck Stewart's calculus. I had to use that shit for calculus 1-3, and couldn't stand it. My instructors hated the book, but it's all my poor-ass high school could afford.

>>	Anonymous Sat Sep 19 22:26:54 2015 No.7539805 >>7529287 Anyone?

>>	Anonymous Sat Sep 19 22:53:10 2015 No.7539845 File: 40 KB, 1296x864, Untitled.png [View same] [iqdb] [saucenao] [google] help i got E for the semi circle but i cant figure out E for the line of charge

>>	Anonymous Sat Sep 19 22:56:20 2015 No.7539853 OP, physical meaning in this context means it is measurable.

>>	Anonymous Sat Sep 19 23:23:55 2015 No.7539881 >>7539805 His proposal probably went nowhere yet

>>	Anonymous Sun Sep 20 00:03:26 2015 No.7539931 >>7539845 use an integral

>>	Anonymous Sun Sep 20 00:10:35 2015 No.7539935 >>7539845 distance of the nearest point of the line times the length of the line then add it to one half the difference of the furthest and nearest points from you point multiplied by the length of the line. assuming the line is parallel to the point

>>	Anonymous Sun Sep 20 00:19:48 2015 No.7539944 >>7537760 Probably. I mean you are paying for the class afterall. Claim bait and switch.

>>	Anonymous Sun Sep 20 02:18:06 2015 No.7540046 How do we know that pi contains every possible combination of numbers? Just because it's infinite doesn't mean it contains all combinations. 10/3 is infinite, but it doesn't contain all possible combinations.

Anonymous Sun Sep 20 04:34:16 2015 No.7540182

Mercury is less dense at high temperatures than at low temperatures. Suppose you move a mercury barometer from the cold interior of a tightly sealed refrigerator to outdoors on a hot summer day. You find that the column of mercury remains at the same height in the tube.

Compared to the air pressure inside the refrigerator, is the air pressure outdoors (i) higher, (ii) lower, or (iii) the same?
(Ignore the very small change in the dimensions of the glass tube due to the temperature change.)

Anonymous Sun Sep 20 05:11:41 2015 No.7540214

>>7540182
Height of mercury fluid in barometer = h
Acceleration due to gravity =g
Density of mercury (dependent on T) = \rho (T) [/spoiler]
Pressure = P

P=h \rho g[/spoiler]

Fridge:
P_F=h \rho_F g[/spoiler]
Outdoors:
P_O=h \rho_O g[/spoiler]

Therefore:
 \frac{P_O}{P_F}= \frac{\rho_O}{\rho_F}[/spoiler]

The rest is up to you.

>>	Anonymous Sun Sep 20 05:24:26 2015 No.7540227 where can I get some practice on graphin surfaces in 3d? That shit is hard to visualize.

Anonymous Sun Sep 20 05:28:30 2015 No.7540230

>>7540214
Thank you for enlightening me. I'm quite ashamed of the fact that I couldn't think of this simple algebraic manipulation myself.

Since the mercury's density outdoors is lower than its density in the fridge, that would imply the pressure outdoors is (ii) lower.

>>	Anonymous Sun Sep 20 05:30:51 2015 No.7540231 >>7540046 >How do we know that pi contains every possible combination of numbers We don't, we don't know whether pi is normal or not

Anonymous Sun Sep 20 05:47:04 2015 No.7540242 [DELETED]

I'm taking an intro class to machine calculations. I need to calculate how big a piston needs to be to lift one end of a car off the ground.
So far what I've come up with is:

F=p(\pi /4 d^2) \Leftrightarrow d= \frac{2\, \sqrt{F}}{\sqrt{\pi}\, p}[\math]

But I need to use 0.85 bar overpressure, and I'm not really sure how to incorporate that into the above? I'm assuming the force is just mg, where m is half the car's mass. Am I on the right track?[/spoiler]

Anonymous Sun Sep 20 05:53:21 2015 No.7540245

I need to calculate how big a piston needs to be to lift one end of an object off the ground.
So far what I've come up with is:

F=p(\pi /4 d^2) \Leftrightarrow d=\frac{2\,\sqrt{F}}{\sqrt{2}\, p}[/spoiler]

But I need to use overpressure, and I'm not really sure how to incorporate that into the above? Do I just add that to the pressure I have? I haven't worked with it before. I'm assuming the force is just mg, where m is half the object's mass.

>>	Anonymous Sun Sep 20 07:12:32 2015 No.7540307 File: 496 KB, 2480x3508, SN2Reaction.png [View same] [iqdb] [saucenao] [google] Can someone explainto me what I am doing wrong, please? I look at the study guide, but it tells me nothing.

>>	Anonymous Sun Sep 20 11:04:36 2015 No.7540563 >>7538977 >>7538982 Don't you see it, /sci/?

>>	Anonymous Sun Sep 20 11:24:19 2015 No.7540598 Is ((P v R)) a correct sentence? Not sure if the redundant brackets make it wrong.

Anonymous Sun Sep 20 11:38:08 2015 No.7540620

1. In what way is putting a 30 year old paper behind a paywall a positive contribution to science and society in general?
2. Can someone get me a copy of Siu's "every K3 surface is Kähler"? I'm at my home computer, so Springer is being a fucking cunt about it.

>>	Anonymous Sun Sep 20 11:48:38 2015 No.7540631 >>7540598 For all sentences P, (P) is a sentence.

>>	Anonymous Sun Sep 20 11:51:50 2015 No.7540638 If matter can't be created or destroyed, how did the big bang create the universe?

>>	Anonymous Sun Sep 20 12:24:28 2015 No.7540690 >>7540245 Force to lift one end of an object off the ground is dependent on moment arms and center of gravity.

>>	Anonymous Sun Sep 20 13:17:10 2015 No.7540781 >>7540638 >how did the big bang create the universe It didn't. Asking that question alone proves that you don't know anything about the Big Bang.

Anonymous Sun Sep 20 16:01:40 2015 No.7541066

Is it even possible to accurately find all the lower eigenvalues using power iteration? Finding the highest is easy but the lower ones are almost impossible to find accurately and reproducible with different matrices. I read that it is hard to do, but is there a method?

Anonymous Sun Sep 20 16:26:08 2015 No.7541132

>>7529536
I dont know if you can work it out like this without integrals that are literally impossible to solve and that but how I would approach it:
split A into the part left of the position where red and blue cross and the part right of that x-value.
then calculate both of those areas (subtract a function from the other, integrate in the respective interval)
then do the same for B.
then you should have to equations A(a) and B(a) and say 0.5A = B and solve for a
dont know if that solution is realistic but I dont see why it shouldnt work

Anonymous Sun Sep 20 22:35:55 2015 No.7541890

hey guys, quick question.

So if I have the fallowing surface

x^2 + y^2 + z^2 = 1
then I get a graph with it's center at (0,0,0) and radius of 1.

but if I have the fallowing
x^2 + (y^2 - 1) + z^2 = 1

the center is shifted 1 to the right on the y axis yes?

I know this might be a stupid question, but I just can't visualize this shit.

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