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420chan is Getting Overhauled - Changelog/Bug Report/Request Thread (Updated July 26)

Relearning math

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- Wed, 10 Sep 2014 08:12:53 EST D/oQWr2Y No.14356
File: 1410351173283.jpg -(82220B / 80.29KB, 504x470) Thumbnail displayed, click image for full size. Relearning math
I've always been naturally bad at math, I failed algebra 2 twice in highschool because I just couldn't grasp the concepts fast enough. My sister who's a freshman in highschool asked me to help her with her homework, and I didn't know JACK SHIT.

I'm 20 and going to community college for a few courses while I work this upcoming spring, I don't plan to take math right away but is there some sort of program/books that will let me relearn math right from the beginning?
5 posts and 2 images omitted. Click View Thread to read.
Rebecca Chorringfuck - Fri, 03 Oct 2014 11:45:44 EST Z+iZvwQ7 No.14405 Reply
Any site for physics? I'm taking capacitors and shit like that, electricity and magnetism. Need a good website for this stuff, preferably video. Youtube and khanacademy are insufficient.
Clara Crebblechodging - Fri, 03 Oct 2014 17:26:19 EST xvgqavvT No.14408 Reply
Re-learning math:

1) Lial's Basic College Math

This covers Kindergarten - Algebra. All the editions are the same so pirate/buy any of them.

2) Serge Lang's "Basic Mathematics" is great and will cover all you need to go into a rigorous theory based college math class. http://www.amazon.com/Basic-Mathematics-Serge-Lang/dp/0387967877/ref=sr_1_1?ie=UTF8&qid=1412284774&sr=8-1&keywords=serge+langs+basic+mathematics

There's also "No Bullshit Math" which does the same as Serge's book: http://minireference.com/ and Sheldon Axler's "Precalculus" which does the same.

I liked Serge's book. It's written by a Mathematician who doesn't hand hold or do anything else except teach you basic math from an advanced standpoint.. so you learn proper terms of everything and actually understand wtf is going on.

For Calculus I did MIT OpenCourseware 18.01 (Single) and 18.02 (Multi). There are no books, just lectures and assignments. After I did them I wanted to explore proofs more so did 18.014 and 18.024 (Both on the open courseware site). Basically all it consists of is doing a rigorous Calc book where you do a lot of proofs. I did them all in Scheme (because I was also trying to learn how to code). http://ocw.mit.edu/courses/mathematics/18-014-calculus-with-theory-fall-2010/ contains course notes by Munkres!! Awesome.

After Serge's book (and I did some of Sheldon Axler's book too) this was all really easy though some of the proofs get challenging. It was also challenging at first to change everything into Scheme/Lisp to write out and prove functions.

For Physics I did this course: http://theoreticalminimum.com/courses/classical-mechanics/2011/fall by Susskind, which is amazeballs. He teaches you modern physics problems. For Physics part II I did MIT's OCW 8.02 course on Electricity and Magnetism since it was req for future compsci theory courses: http://ocw.mit.edu/courses/physics/8-02sc-physics-ii-electricity-and-magnetism-fall-2010/

I did all this so I could do SICM, Structural Interpretation of Classical Mechanics which is like working with magic https://mitpress.mit.edu/sites/default/files/titles/content/sicm/book.html

negative binomial help

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- Fri, 03 Oct 2014 15:03:16 EST Aql4bjnf No.14406
File: 1412362996183.png -(3140B / 3.07KB, 458x381) Thumbnail displayed, click image for full size. negative binomial help
I'm trying to get the variance for hypergeometric discrete random variable without using the moment generating function and am having a lot of trouble.. I started with V(X)= E(X^2) - E(X)^2 and can get E(X)^2 but can't get E(X^2). Then someone suggested I try E(X(X+1)) but I don't understand how to do that.... Any help?

Clarification on velocity vector and acceleration

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- Mon, 29 Sep 2014 17:57:44 EST dfurG/DB No.14392
File: 1412027864973.gif -(426031B / 416.05KB, 667x488) Thumbnail displayed, click image for full size. Clarification on velocity vector and acceleration
The problem is below; what my question is, is do I need to know t or what? If I don't, then what do I do and if I do need it, how do I find it?

At a certain moment, a particle moving along a path has a velocity v=<3,2,1> and a=<0,5,2>. Find T, N and the decomposition of a into tangential and normal components.

If I had a parametrized function for v I'd be good, but I don't because I don't know t...
Any help?
Fanny Nendlefetch - Mon, 29 Sep 2014 19:38:38 EST dfurG/DB No.14393 Reply
fac u op
Nell Foshfield - Wed, 01 Oct 2014 06:50:01 EST Gw2IN3ba No.14402 Reply
If by t you mean time, they don't provide that information and there is no way to deduce it. T here is kinetic energy and N is the normal force, yes? All you need to find T is the velocity and the mass (I assume the mass was provided earlier). Because the velocity must be tangential to the path at the point under consideration, you can use this to find the tangential and normal components of a. And the normal force is just the normal component of a scaled by m.
John Fendernidge - Wed, 01 Oct 2014 22:27:34 EST kDYSaBHq No.14404 Reply
To find tangential acceleration just project the a vector onto v

a_tan = a dot v/||v||

Then a_norm = a - a_tan

yay math

Help, what the fuck is P?

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- Thu, 25 Sep 2014 01:46:11 EST aQ2ap22j No.14379
File: 1411623971598.png -(17447B / 17.04KB, 753x627) Thumbnail displayed, click image for full size. Help, what the fuck is P?
How do I solve these?
Or what are the solutions?
5 posts omitted. Click View Thread to read.
Martha Donkinherk - Mon, 29 Sep 2014 23:01:21 EST umZ//85N No.14394 Reply
1st one,
x-y <=4

use above two equations, solve for y
y<= 6 - x
y >= x - 4
y>= 0
since x <=5, and x-4 <= y, then the maximum of y is 1, thus we know
0<= y <= 1
at this point i think x is unbounded, meaning that P has no minima
but the maximum is x = 5 and y - 1 so Max P = 20
John Fendernidge - Wed, 01 Oct 2014 22:24:51 EST kDYSaBHq No.14403 Reply
lol you were right the first time. For your example the maximum is at one of the corners, x=y=-10

Linear Algebra and Matrices

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- Mon, 29 Sep 2014 23:56:43 EST wV5uRW/L No.14395
File: 1412049403600.jpg -(19820B / 19.36KB, 378x246) Thumbnail displayed, click image for full size. Linear Algebra and Matrices
Hey guys, first post in /math/, hope you guys can help me out. Right now in Linear Algebra we're working with matrices (no surprises there) and I'm pretty confused on how to even begin solving this problem. We just recently learned about inverse matrices, transposed matrices, and matrix multiplication. Appreciate any guidance.
1 posts omitted. Click View Thread to read.
Lillian Druddledone - Tue, 30 Sep 2014 14:51:18 EST wV5uRW/L No.14400 Reply
Thanks for the tip, but I feel like matrices act differently. So I want to put the X's on the same side, but can I add/subtract the two matrices together?
Samuel Windledat - Tue, 30 Sep 2014 20:27:49 EST V2nhYpJ2 No.14401 Reply
IIRC that property is called distributivy and that should hold with matrix multiplication. Or I might be wrong.
driven !FTPgBqDDy. - Sat, 04 Oct 2014 23:07:55 EST MSWrPT9p No.14409 Reply
OP you need to group the X terms on one side, find the inverse of the matrix multiplying X (there is a formula for 2x2 matrix inverse), and then multiply both sides by the inverse yielding X = somematrix.

'cos a matrix multiplied by its inverse is the identity matrix.
and the identity matrix times X is just X, it's 1 in matrix terms.

What does this mesn?

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- Tue, 30 Sep 2014 10:01:26 EST Vib06tOc No.14398
File: 1412085686890.png -(4902B / 4.79KB, 389x248) Thumbnail displayed, click image for full size. What does this mesn?
Wesley Huffingbanks - Tue, 30 Sep 2014 10:34:08 EST aO+d5dci No.14399 Reply
first equation is called the gaussian integral, it's basically that the area under the curve y = exp(-x^2) is the square root of pi.

second equation is the fourier series of f(x), this is basically saying that you can write the function f as a infinite sum of sines and cosines.

last equation is the quadratic formula, it gives the solutions of ax^2+bx+c=0 , where a,b,c are real numbers.

favorite and least favorite math stuff

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- Fri, 22 Aug 2014 05:21:14 EST Z8nJxYf6 No.14298
File: 1408699274913.jpg -(79045B / 77.19KB, 510x310) Thumbnail displayed, click image for full size. favorite and least favorite math stuff
What's your favorite math subject? and your least favorite?

I'm taking a re-exam for one of my math classes (4th time I do this shit), and it's some basic billiondimensional stuff, you know the kind. Anyway, I love the lagrange multiplier stuff, and the stuff that can be expressed equally as an analisys problam as well as a linear algebra problem. But those fucking integrals!
It's just so fucking tedious. We're even allowed to use maple for the full duration of the exam, and still; Bweeurg!

But discrete maths, that's fucking delightful! Galois fields and stuff, waw! Also, probability theory has some really cool proofs and results, too bad I only have 2 classes on it.
7 posts omitted. Click View Thread to read.
Hannah Penningcocke - Fri, 19 Sep 2014 11:12:36 EST AJrEUkAQ No.14368 Reply
1411139556215.png -(179035B / 174.84KB, 318x324) Thumbnail displayed, click image for full size.
I loved geometry. I wish I remembered all of those damn theorems and postulates I learned as a freshman in high school. Alas, I dropped out and forgot 80% of them. Regaining my math knowledge, though!

I'm not sure what I dislike the most. I'm still a math babby.
Sophie Gicklestock - Sat, 27 Sep 2014 09:02:36 EST vsyqzWjr No.14384 Reply
Graph Theory and Abstract Algebra are my favorites. My least favorite might be Real Analysis? It's all super useful and interesting stuff in its own special kind of way, but can be tedious and not fun to write proofs.
Nigger Congerchuck - Sat, 27 Sep 2014 13:19:49 EST V2nhYpJ2 No.14385 Reply
Favourite thing I've been taught in math courses would likely be probabilites.
3D geometry in game design was fun too. Maybe the most interesting (and most 'mathy') stuff was in modelling parallel programs with composed state machines.

slope wtf

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- Mon, 22 Sep 2014 04:33:46 EST qmsb2zs3 No.14375
File: 1411374826804.png -(9798B / 9.57KB, 241x167) Thumbnail displayed, click image for full size. slope wtf
I have no idea what I'm doing here. The problem says "Find the slope of the line containing the given points" All examples in the book are completely different. The answer to 27 is 5, but I have no idea why. How do I do these problems?
Oliver Hellyman - Mon, 22 Sep 2014 04:44:25 EST qmsb2zs3 No.14376 Reply
shit I'm retarded they're ordered pairs


Proofs are the shit

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- Fri, 12 Sep 2014 20:51:34 EST TrfloaeP No.14361
File: 1410569494767.jpg -(65377B / 63.84KB, 620x468) Thumbnail displayed, click image for full size. Proofs are the shit
Sup guys. I'm a couple weeks into my first MATH class that is based around proofs and it turns out I'm fucking awesome at this type of thing. I had a very difficult time learning Cal2 and Cal3 because of poor quality of previous education, other factors, etc.

So, my question to you guys is, what do the people that are naturals when it comes to the formal proof methodology of thinking do? What kind of career should I be focused on, and what are other classes that are similar to this type of thing? I know it will depend on university wrt names of classes, but I have heard Modern Algebra is one of them and Real Analysis is another.

I'm also interested in "Set Theory", but do not know where to start or if/how it relates to proofs.. Thanks.
Fucking Badgestone - Sat, 13 Sep 2014 00:26:31 EST Hs5ANTy/ No.14363 Reply
I don't have the energy to rant to you about what constitutes good mathematics right now, but math is basically all about defining things and then proving things about them. If you really like this stuff, consider becoming a mathematician.
Molly Sacklestotch - Sat, 13 Sep 2014 19:01:40 EST VWxuWxBu No.14365 Reply
If you *really* like proofs (and want to learn about formal proofs), than you should take logic and set theory (although it is possible to like logic and not set theory)

Should I be a numerologist?

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- Thu, 28 Aug 2014 00:14:38 EST NE+OsI8C No.14331
File: 1409199278216.jpg -(214894B / 209.86KB, 1003x1400) Thumbnail displayed, click image for full size. Should I be a numerologist?
I look at math equations and I read aloud what pertains to the universe (1 and or/2 [in the future which is the past])

I just write out simple math equations


1+1 = life, 2=life with god, 2+2 = universal communication. and there are many more outcomes, simply one for each individual for those simple equations.

Its like I can peer into the soul of other people with math.

Lately, my math equation of my life = 2+2=5 (1 being innate, the universe) waiting for it to become 2+2=6. (when 1+1 (FOR HOW DOES ONE BECOME TWO WITHOUT BEING ONE ITSELF) becomes the new innate and we shift into the next predestination by means of a new god)

More info on 2+2=5 is I died, saw the universe, deemed everythings plural, thus attempting to recreate my lifes equation into 2+2=6.

Have some hayley.
8 posts omitted. Click View Thread to read.
Clara Gemblewill - Thu, 04 Sep 2014 01:57:37 EST qt5i3eqa No.14348 Reply
Are you Doctor? From /psy/? You are aren't you? Your schizophrenic ramblings are structured exactly like Doctor's were.
Lillian Crellerbutch - Fri, 05 Sep 2014 00:45:33 EST gzRif05L No.14349 Reply
1409892333868.gif -(3040265B / 2.90MB, 200x170) Thumbnail displayed, click image for full size.

>Should I be a numerologist?

Sure. Be a numerologist.
But see a psychiatrist.

The delusions you're posting here seem pretty harmless, but you need to be monitored in case they turn into something that will cause you to harm yourself.
Henry Momblewetch - Wed, 10 Sep 2014 13:54:16 EST 8Zy6ydRZ No.14357 Reply
ur doing it wrong though OP & making me cringe a bit

At least study the history of numerology, sacred geometry, & alchemy. Listen to some Manly P Hall history lectures.

see you on /spooky/

help, precalc final tomorrow

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- Mon, 25 Aug 2014 22:37:15 EST kQQi+WA1 No.14313
File: 1409020635976.jpg -(26366B / 25.75KB, 347x498) Thumbnail displayed, click image for full size. help, precalc final tomorrow
One thing I want to work on is these box construction problems.
A box is being constructed by cutting 2 inch squares from the corners of a rectangular sheet of metal that is six inches longer than it is wide. If the box is to have a volume of 270 cubic inches, find the dimensions of the metal sheet.
L = W+6
H = 2
Does the volume, 270 = (w-4)(w+2)2 ???
How do i set this up? is that right? would appreciate as much help as you can give. Thanks!
8 posts and 1 images omitted. Click View Thread to read.
Isabella Lightcocke - Wed, 27 Aug 2014 15:55:43 EST Gw2IN3ba No.14328 Reply
1409169343239.jpg -(47646B / 46.53KB, 450x308) Thumbnail displayed, click image for full size.
I never took trig nor precalc - in highschool or college. Hell, I just skipped my last two years of highschool. I took a placement test and was allowed to go straight into calculus. What little trig I needed to know for calculus was in an appendix at the back of my calculus book. I was taught the basics of trig in geometry anyway; and I taught myself the derivations of the identities I wasn't familiar with. IMO, devoting your time to an entire course in trig is a waste.
Nathaniel Pemmlestone - Wed, 27 Aug 2014 19:48:07 EST BJycWA4m No.14330 Reply
I fucking loved this problem back in precalc because I understood before anyone.

Those were the good days
Martha Clandleford - Thu, 28 Aug 2014 13:59:18 EST kQQi+WA1 No.14333 Reply
Aced the precalc final. was really pretty easy. yay!
anyway, i think i will be studying trig over the break with that girl, that way i can i can go straight to calculus!
Math rocks!!!

Math Placement Test Shit

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- Tue, 26 Aug 2014 21:43:16 EST NuE2NaRH No.14320
File: 1409103796629.jpg -(116317B / 113.59KB, 853x648) Thumbnail displayed, click image for full size. Math Placement Test Shit
I'll spare you the details and tell you my basic situation. I'm a 2nd year college student at a community college and in order to graduate in a timely manner I need to take Pre-Calculus. Problem is I don't have the math requirements to do it, so I need to re-take a placement test in order to get a good enough grade to take it.

I have a couple study guides with example questions and such so there's basic arithmetic (addition, decimals, fractions, etc.) and things like rational numbers, polynomials, quadratics, scientific notation, factoring (honestly I could probably scan the study guide if someone really wanted me to).

I was curious if anyone had any specific studying advice or really anything remotely useful because I'm freaking out about this because this shit is pretty goddamn important.
1 posts omitted. Click View Thread to read.
Ernest Decklefield - Tue, 26 Aug 2014 23:20:29 EST kQQi+WA1 No.14322 Reply
and yeah, if you can do everything on the study guide, you should be fine. I never got a study guide. i'm really tired though, so i might not know what i'm talking about.
I'm stressing about my precalc final. If I have 84 % in the class right now, and the test is worth 30%. what kind of grade do i need to get an A, or B?
Fuck! Horsepiss! Son of a two balled bitch!
Have you seen Snuff Box, OP?
Ernest Decklefield - Tue, 26 Aug 2014 23:38:43 EST kQQi+WA1 No.14323 Reply
But seriously, you should be able to talk a counselor into letting you take precalc
Fanny Duckfuck - Wed, 27 Aug 2014 07:26:41 EST NuE2NaRH No.14325 Reply
I already talked to them about taking precalc but basically they're not allowed to unless I have a kind of "math proficiency score" above a certain level.

And there isn't like a letter grade it's just like a score. I have no idea how it works but I know need to get like over a 31 or something.

Cute little abstract algebra thing

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- Mon, 25 Aug 2014 00:34:32 EST yGgK6aCs No.14307
File: 1408941272614.jpg -(76692B / 74.89KB, 600x398) Thumbnail displayed, click image for full size. Cute little abstract algebra thing
If you define an inverse operation as (in addition notation):
a + b = a + (-b), then the inverse operation is never commutative
(a - b does not equal b - a)
regardless of the status of the original operator unless both of those elements are identical.
I smoked nicotine, cannabis, drank coffee and went for a walk while listening to Terence Mckenna and this literally fell out of my head. Is this right? If you wrote the inverses of the inverse operation expressions, they're different unless the elements are identical, in which case it returns the identity element. You guys ever realize really specific shit like this while out and about?
Albert Fellerstock - Mon, 25 Aug 2014 05:46:37 EST V9psgK+4 No.14309 Reply
If you used the multiplicative notation, this result would appear far more intuitive.

a/b = b/a if and only if a = b.

I love getting those realizations out of the blue. It's even better when I'm intoxicated.
Alice Mussletere - Mon, 25 Aug 2014 09:02:33 EST EvoUDt1O No.14310 Reply
This is false. Consider that a/b=b/a is true as long as a^2=b^2. So if we let a=-1 and b=1 then our statement is true but a and b are not equal.

I'm sure you can think of more examples.

swarm theory

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- Thu, 21 Aug 2014 06:36:18 EST tzbijKoV No.14295
File: 1408617378218.jpg -(22629B / 22.10KB, 227x173) Thumbnail displayed, click image for full size. swarm theory
posted on /chem/ as well but i know there are formulas for this. langtons ant being the one dimensional precursor.

does anyone have a clue as to where i can read actual numbers on this?

also, as always; discuss
Eugene Snodridge - Fri, 22 Aug 2014 20:16:12 EST 0P74hB5y No.14299 Reply
idefk but damn that game of life....
Edwin Fonningdock - Sat, 23 Aug 2014 10:53:22 EST orekpRAb No.14301 Reply
Cellular automata is a basic implementation of swarm intelligence

It's more of a state-based computational thing than a numbers thing

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