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Sett theory by Graham Fingerhat - Thu, 01 Sep 2016 05:16:48 EST ID:NsqdJ6Lc No.15184 Ignore Report Reply Quick Reply
File: 1472721408300.jpg -(2195808B / 2.09MB, 3920x2204) Thumbnail displayed, click image for full size. 2195808
Is there a way to find the equivalence relation corresponding to any partition?
Like p = {{1,4,7},{2,5,8},{3,6},{9}} with is an example i have in front of my nose. Can I find the relation from wich i get that partition of {1,2,3,4,5,6,7,8,9} ?
For the record I think not, but I only read about this stuff last night.
3 posts omitted. Click Reply to view.
Archie Gussleham - Sun, 04 Sep 2016 16:26:12 EST ID:d7aT3WKf No.15188 Ignore Report Quick Reply
Hahaha, great answer mr. Robot
Archie Gussleham - Sun, 04 Sep 2016 16:33:07 EST ID:d7aT3WKf No.15189 Ignore Report Quick Reply
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Charlotte Gobberhood - Tue, 06 Sep 2016 18:06:06 EST ID:4JPlB6jB No.15190 Ignore Report Quick Reply
>This is the same as having that b in P_i and a in P_i, so (b,a) in R, so the relation R is reflexive.
This should say symmetric at the end instead of reflexive.

>manually define an equivalence
Do you mean the realtion induced by a partition or something else? I'm not sure what constitutes "manually" defining a relation. Also, it's not rigorous to say that
>numbers are in the equivalence class here if they are 3 more than some other number in the equilance class
since the partition {{1,4,7},{2,5,8},{3,6,8}} also has that property and induces a different equivalence relation.
Charlotte Gobberhood - Tue, 06 Sep 2016 18:07:01 EST ID:4JPlB6jB No.15191 Ignore Report Quick Reply
This should be {{1,4,7},{2,5,8},{3,6,9}} obviously.
Nathaniel Fembledatch - Wed, 07 Sep 2016 18:46:55 EST ID:DsqbErs4 No.15193 Ignore Report Quick Reply

Oh I misread the OP, you're right. What I mean by manually defining an equivalence is to identify all the elements of one of partition sets. You could rephrase what I said by identifying the orbits of the action of adding 3 to elements of the set, with the caveat that 9 is in its own equivalence class separate from everyone else.

A Geometry(?) Question by Henry Bugglewill - Thu, 31 Mar 2016 20:43:14 EST ID:Z131bdYa No.15075 Ignore Report Reply Quick Reply
File: 1459471394809.jpg -(163021B / 159.20KB, 1294x1294) Thumbnail displayed, click image for full size. 163021
What is the mathematical/geometric name for the shape of a peanut butter cup like this?

The best I can come up with is "crennelated truncated cone" but I feel like there's some ten-word name I could use that would very accurately describe it....
4 posts and 2 images omitted. Click Reply to view.
Charlotte Neshgold - Sun, 03 Apr 2016 23:29:07 EST ID:Z131bdYa No.15082 Ignore Report Quick Reply
That sounds super epic and all, but I'm a chemist not a mathematician :/
Cyril Dibblespear - Tue, 19 Apr 2016 05:00:58 EST ID:npKQem+e No.15095 Ignore Report Quick Reply
Fuck you, now I have gone into chocolate relapse.
Molly Suvingham - Tue, 19 Apr 2016 21:39:48 EST ID:dFkJK1jc No.15096 Ignore Report Quick Reply
should call it the Reese Cup. if anyone's qualified to name it it's us
Nell Penderfedging - Sun, 15 May 2016 20:38:08 EST ID:1eeqYqTy No.15117 Ignore Report Quick Reply
Upside down star fort.
John Funkinshaw - Thu, 25 Aug 2016 10:53:32 EST ID:n7MnP1ar No.15182 Ignore Report Quick Reply
crennelated frustum

Probability question (probably beneath most you) by Esther Dirringlore - Mon, 16 Nov 2015 07:50:43 EST ID:TdrCDJzk No.14973 Ignore Report Reply Quick Reply
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I'd appreciate it if someone could answer a probability question for me. I can't remember exactly how to work it out.

Question: How many combinations of 3As and 5Bs are there? For example, one combination would be: 'AAABBBBB' ; another would be 'ABABABBB'.
1 posts omitted. Click Reply to view.
Lillian Povingstone - Mon, 16 Nov 2015 23:18:29 EST ID:TdrCDJzk No.14975 Ignore Report Quick Reply
Yeah, if I've understood it correctly I should have said permutations. There would be 8 digits in the sequence. 3 of them would be 'A', 3 would be 'B'. So my question is, how many permutations?

8-0 1
7-1 8
6-2 28
5-3 ?
4-4 n/a
3-5 ?
2-6 28
1-7 8
0-8 1

I hope that's made it a little clearer. Thanks.
Lillian Povingstone - Tue, 17 Nov 2015 00:46:25 EST ID:TdrCDJzk No.14976 Ignore Report Quick Reply
I meant 3 would be 'A', 5 would be 'B'
Lillian Povingstone - Tue, 17 Nov 2015 01:03:27 EST ID:TdrCDJzk No.14977 Ignore Report Quick Reply
Okay. Ignore this thread. I found an online combinations calculator.
Whitey Gobbleson - Tue, 17 Nov 2015 14:30:55 EST ID:J4OUpAxW No.14978 Ignore Report Quick Reply
Magnets how do they work?
John Divingmetch - Tue, 23 Aug 2016 13:31:10 EST ID:TANb9lmN No.15181 Ignore Report Quick Reply

Help me help someone get a math-boner by Hannah Sollernodge - Fri, 22 Apr 2016 13:02:27 EST ID:WD6PkLOh No.15100 Ignore Report Reply Quick Reply
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Ok, so how would you introduce someone to the fun bits of mathematics? My girlfriend has maths at standard grade (8/9th grade for Americans I think), and she's interested in seeing why I do it just for fun. She isn't too patient with it, I tried to explain that x^1/3 is the cube root of x and she just got angry after a while and quit, so it needs to have the most 'wow' for the least amount of difficulty (basically math porn). I was going to show her some very basic calculus and some quadratic equation shit, but I'm doubting myself now.
What should I be showing her, or is it a lost cause?
11 posts and 4 images omitted. Click Reply to view.
Jack Chittingfoot - Fri, 20 May 2016 07:01:13 EST ID:3oORF0f9 No.15124 Ignore Report Quick Reply
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You can stop trying to cling to realism. I find the symmetry of networks and trees to be really intriguing and beautiful, but when someone asks me what purpose my funny little doodles do to serve mankind, I tell them to go fuck a landmine.

Also, you shouldn't try to be math-buddies with someone who's a different kind of problem solver than you are. If you don't agree on how problems should be reasoned about, you're not gonna work well together, unless you're both very experienced in mathematics.

Try learning something new together rather than teaching her something that you already know. Looking Glass Universe had this really fun puzzle where you have to solve the EPR paradox and derive Bell's Theorem. You shouldn't look up either of those things if you want to have maximum fun.

Geometry and topology make for very good visual entertainment.
Step one: cut some A4 paper evenly into 8 long strips.
step two: glue two strips together to make a '+' sign.
step three: bend one piece into a mobius strip. Note the chirality of this mobius strip.
step four: bend the second piece into a mobius strip of opposite chirality.
step five: split both mobius strips.
The results will surprise you.
Comment too long. Click here to view the full text.
Priscilla Pinkinstone - Sat, 16 Jul 2016 01:41:16 EST ID:Tg2WbKCI No.15176 Ignore Report Quick Reply
good writing is(should be) practically as universal as 1+1=2, after all, we ideally should communicate truth with language.

in practice this rare, as the implications of certain ideas frighten, and are shut out with mockery
Martin Goodfoot - Sun, 17 Jul 2016 21:20:51 EST ID:9K7KtQWq No.15177 Ignore Report Quick Reply
explain what she enjoys in terms of math. Whenever I tell people you can explain biology/taxes/cooking in terms of math they get intrigued.
George Gennerstock - Mon, 01 Aug 2016 12:05:29 EST ID:yxQzbAra No.15178 Ignore Report Quick Reply
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I have the same problem. I can't seem to be all that interested in mathematics. The only thing that serves as a motivation is when I solve a problem, which I see as moderate to hard, by myself. Too bad I am bad at maths, so that dopamine release doesn't happen a lot. I see the proposal of mixing maths with something you find genuinely interesting being mentioned. The only thing is, I find everything from astronomy and botany to politics and art interesting. I do not have many hobbies, because I usually lose interest in them after a period. I have brewed, planted, and written graffiti, but they never stick for more than a few projects.
How do I get myself interested in the amazing world of mathematics? I really want to be able to do complex equations one day. Is it really nothing else than forcing myself to do a few problems every day? I have the attention span of a pornstar's pubic hair, so I don't think that will work for me.
Shit Benningbury - Sat, 06 Aug 2016 03:29:45 EST ID:ijd+nKqH No.15180 Ignore Report Quick Reply
Measurement by Lockhart

Here's Looking at Euclid by Bellos

Patterns of the Universe: A Coloring Adventure in Math and Beauty by Bellos
Find it on amazon, interesting math colouring book where you reveal patterns.

Loop, the game
http://www.loop-the-game.com/ Bellos also reinvented pool using an ellipse

Riddle your diddle by Archie Nemmerhock - Tue, 05 Apr 2016 18:49:37 EST ID:cTPi6AuQ No.15083 Ignore Report Reply Quick Reply
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There's two guys:
If guy #1 borrows 2 dollars from guy #2, they have the same amount.
If guy #2 borrows 2 dollars from guy #1. he has twice the amount of guy #1.
How much money do they have from the start?
1 posts and 1 images omitted. Click Reply to view.
Phoebe Brookwater - Sat, 09 Apr 2016 19:05:24 EST ID:cTPi6AuQ No.15086 Ignore Report Quick Reply
Yes, I am actually 12 years old and currently attending middle school.
I thought this thread would be super stoked on me and all like "wooow, I can't figure it out. Wooow, dude, what is this? wooow"

Fuck all y'all nb
User was banned for this post
User was banned by: Lekta
Reason: See you in 6 years.
Whitey Socklesick - Sun, 10 Apr 2016 15:05:44 EST ID:mUpp8lCW No.15088 Ignore Report Quick Reply

To actually solve by showing work

x = guy 1
y = guy 2

Statement 1
(*) x + 2 = y - 2
(x borrows 2, so he has +2, y lends 2 so he is -2)

Statement 2
2*(x-2) = y + 2
(**)2x - 4 = y + 2
Comment too long. Click here to view the full text.
Phyllis Nivingshit - Mon, 11 Apr 2016 07:47:21 EST ID:A2j/BW/W No.15089 Ignore Report Quick Reply
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Wow! Such math! So amaze! Wow!
Phineas Condlenore - Sat, 07 May 2016 17:02:14 EST ID:3U6ZTH6i No.15114 Ignore Report Quick Reply
Lekta thought Phoebe was serious...

Lekta should be a cop.
Priscilla Pinkinstone - Sat, 16 Jul 2016 01:31:09 EST ID:Tg2WbKCI No.15175 Ignore Report Quick Reply
poor guy skipped reading comprehension class, wait that isn't real, you should still feel bad

Gamedev is great by Ian Dundleludging - Wed, 04 May 2016 00:31:32 EST ID:7yI2oiC+ No.15109 Ignore Report Reply Quick Reply
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it's a great way to see the impact of changes in your model. Of course this applies mostly to folks interested in applied mathematics. But what is "pure" mathematics, but math that hasn't been yet applied? Give me a physical interpretation of the fractional calculus. Better yet, show me it in a Game.

There's also the fact that a lot of gamedevs struggle with some basic maths, mostly stuff regarding linalg, quaternions come up a lot. You could probably help!

Did you know: There's a 420chan amateur gamedev community, >>>/vg/664016

And from a pedagogical pov, who'd bet against gamedev working its way into the classroom? It's the perfect confluence of any applied area you can think of, Fourier series to taxicab metric
Clara Fadgebit - Fri, 20 May 2016 17:24:26 EST ID:WHIrmu8h No.15127 Ignore Report Quick Reply
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> gamedev in the classroom

It would take the fun out of it eventually if it's forced. My first program was a game and later gamedev had me apply trig. It is still a lot of boring work, too, a lot of pure programming, so to speak, as pure maths is applied to maths.

Planning is required when fleshing out an game from scratch. There could be too much freedom in a project to grade it. Gamification works better if fit to the audience, eg. in a logic puzzle game.
Ian Goodworth - Sat, 11 Jun 2016 17:23:59 EST ID:+Gs8DK3Y No.15159 Ignore Report Quick Reply
True, making games is lots of programming and boring work until you get the interesting math part.

I think programming shaders is a better way of teaching maths https://www.youtube.com/watch?v=0ifChJ0nJfM
And to be honest most maths you will do in gamedev has to do with graphics.
Shitting Crimmerfield - Mon, 20 Jun 2016 01:47:59 EST ID:ZiObD4pn No.15173 Ignore Report Quick Reply
Maybe gamedev isn't that good for applying maths, but I'm pretty sure it's good for making physics simulations.

How do I recover the signs of integrals and derivatives? by Nell Penderfedging - Sun, 15 May 2016 20:44:52 EST ID:1eeqYqTy No.15118 Ignore Report Reply Quick Reply
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I can define derivatives and integrals in terms of the Lebesgue
measure but how do I recover signs?

$$ \left. \left\lvert \frac{\mathrm{d} y}{\mathrm{d} x} \right\rvert \right\rvert_{x = a}=
\lim_{C \rightarrow \left\{a\right\}}\frac{\lambda^*\left( \left\{ y_x \, \vert \, x \in C \right\} \right)}{\lambda^*\left( C \right)} $$

$$ \left\lvert \, \underset{\, \, x \in C}{\int} y \, \mathrm{d} x \right\rvert =
\lambda^* \left( \left\{ \left( x , y_x \right) \, \vert \, x \in C \right\} \right) $$
Martha Pudgestedging - Tue, 14 Jun 2016 12:22:55 EST ID:c7Q4EFJt No.15163 Ignore Report Quick Reply
So there's two ways to do this. The first is to define the integral in terms of the lebesgue measure and use the doublet distribution to define the derivative in terms of an integral transform and the second is to define a delta as the lebesgue measure of the increasing sections of a function minus the measure of the decreasing sections of a function and then define the derivative using the delta as normal.

Mathemusings by Betsy Puffingspear - Wed, 08 Jun 2016 18:56:24 EST ID:3U6ZTH6i No.15153 Ignore Report Reply Quick Reply
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Hey, I thought this board would appreciate this question the most.

So you lightly press your fingers on a string to play the harmonic.
(I'm gonna pretend i have a c-string on my guitar because all the tables you will find lists c as the root note).

Lets say you play the 5th harmonic, lightly press 1/5 of the way from one end.
You hear an E, the 5/4 interval to C
The 3rd harmonic, a G, the 3/2 interval

This could lead me to believe that if I play the 7th harmonic,
I would get the 7/6 interval, somewhere between D and D#

But I what i hear is something slightly lower than A# (or Bb if you will)

I'm thinking it's because 6 is not a square number.
Comment too long. Click here to view the full text.
Hugh Sessledock - Thu, 09 Jun 2016 03:14:56 EST ID:lYjTKStM No.15154 Ignore Report Quick Reply
99% of modern instruments are tuned to equal temperament.
That means each half-tone is separated by adjacent ones by a ratio of 2^(1/12).

This also means that every interval (besides whole octaves) to an irrational number.
So when you go up/down musical intervals you end up precisely where you started if the number of steps up/down are the same. This however means through that notes will sound slightly off to natural notes.

I don't know if that answers you question:
Clara Grimridge - Thu, 09 Jun 2016 06:33:41 EST ID:3U6ZTH6i No.15155 Ignore Report Quick Reply
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Well aware of the equal temperament thing.
I also know that the 1/7 harmonic is not used in most Just Intonation tunings.
I'm talking about the actual harmonic to interval relation.
I kinda expected the 7/6 interval, 7 being the root note (the whole string) and 6 being the note I hear from pinching that whole string 1/7 of the way from the end.
(6/7 of the way from the other end ofc)
What I hear is closer to a 16/9 interval (I think it's slightly lower)

I'm pretty sure it's because six times a seventh does not produce an octave of a seventh, like a square number would.

Still I am unable to form a good theory of what's happening.
James Trotman - Tue, 14 Jun 2016 16:46:24 EST ID:3U6ZTH6i No.15164 Ignore Report Quick Reply
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Well if anyone cares, I figured it out to my satisfaction.
4 being the closest square number; 4 sevenths of the string, bringing out the 7/4 interval of C, the flat Bb; is the one ringing out the most when I pinch a seventh.
Was pretty obvious in hindsight. nb.

Generating Polynomial by Cedric Mavingwell - Fri, 03 Jun 2016 05:39:35 EST ID:FvfJV3ZM No.15146 Ignore Report Reply Quick Reply
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Can anyone shed some light? I thought I just had to substitute powers of t into this equation to get the answer. Am I missing something stupidly obvious? I just can't get to the first line of the answer. http://imgur.com/a/9iWQ1
Hannah Gattingmot - Fri, 03 Jun 2016 11:53:21 EST ID:A2j/BW/W No.15147 Ignore Report Quick Reply
You have to use Taylor expansions. So the first step is to substitute the Taylor expansion for the exponential function. Then you substitute the Taylor expansions for the different powers of the (1-t) terms. Then you group like powers of t. Whoever wrote the solution fucked up by squaring the t inside the parentheses in the third line btw, but they still got the correct result.
Reuben Pittwill - Sat, 04 Jun 2016 04:44:18 EST ID:Ktnbl7MZ No.15148 Ignore Report Quick Reply
>>15147 Thank you mate.
Phoebe Dimmerpuck - Sat, 04 Jun 2016 12:19:38 EST ID:A2j/BW/W No.15149 Ignore Report Quick Reply
No prob.

Probability by Jack Bloffinghood - Sun, 29 May 2016 19:59:52 EST ID:lgvPZ+E8 No.15140 Ignore Report Reply Quick Reply
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How do you solve these types of problems:

Lets say you have a chicken who, on average, lays 1 egg per day.
After 7 days what is the probability that the chicken will have laid at least n eggs?
Hannah Daffingway - Mon, 30 May 2016 11:31:43 EST ID:lYjTKStM No.15141 Ignore Report Quick Reply
You need to know which probability distribution and it's parameters.
Most examples assume a normal distribution, but even then you need to know it's sigma value.
Of course it would be interesting to solve the differential equation for al sigma values and number of eggs.
Phyllis Soblingnedge - Mon, 30 May 2016 11:33:06 EST ID:A2j/BW/W No.15142 Ignore Report Quick Reply
Eliza Crabblewater - Mon, 30 May 2016 21:48:39 EST ID:lgvPZ+E8 No.15143 Ignore Report Quick Reply
1464659319762.gif -(4642823B / 4.43MB, 500x500) Thumbnail displayed, click image for full size.

I did the calculations using a Poisson distribution and it seems to be working great. The actual average is nice and close the expected average whether I set lambda to 5 or 5000.

pic related

Help explain Principal Component Analysis to a dummy by Oliver Lighthall - Tue, 10 May 2016 12:55:53 EST ID:xd9SEzRh No.15116 Ignore Report Reply Quick Reply
File: 1462899353126.gif -(21904B / 21.39KB, 505x369) Thumbnail displayed, click image for full size. 21904
Hey guys,

I don't know anything about Principal Component Analysis (PCA) but I'd like to learn. Can someone explain to me the PCA algorithm (the algorithm to find the set of PCA vectors) for operating on a 2D set of real data?

Here's my understanding of it so far (feel free to add corrections):
  • First you have to normalize your set of real datapoints because PCA works best on normalized datapoints
  • Then, calculate the mean of the data-set (this is just the flat-average of the various components of the data). So in R2 for instance, this is (x1 + x2 + x3 +...) / (n) and (y1 + y2 + y3 + ...) / (n) for finding the mean X-value and mean Y-value.
  • Next, subtract the mean from the data-points. This centers the data around the origin.
  • Then we begin calculating the variance-covariance matrix, which we're going to use as part of the PCA algorithm
  • Variance of each datapoint is calculated as the "average squared deviation from the mean" which is in this case (the case of already having subtracted the mean from each datapoint) we can simply square each datapoint, then divide by the number of datapoints to find its variance (is this even correct?)
  • Then you have to calculate the covariance (I'm really fuzzy on how to do this part given our initial dataset).
  • Next step is to assemble the variances and covariances that we have calculated into the variance-covariance matrix
  • Then you calculate the eigenvectors and eigenvalues of the variance-covariance matrix. There should be one eigenvector (and each eigenvelue corresponds to one eigenvector) for each dimension in the original dataset (so for 3 dimensional data, you should get 3 eigenvectors).
  • Then for PCA, you sort the eigenvectors by their eigenvalues to find the principal components. The principal components' vectors are the eigenvectors we calculated in the previous step.

Is this right? Can someone explain this to me more simply?

Fuck squares by Isaac Newton - Sat, 07 May 2016 01:20:21 EST ID:HaG6KVm7 No.15112 Ignore Report Reply Quick Reply
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I fucking hate squares and shit.

That's why I made apples into circles, they use to be fucking square.

Can Math Ban Me? Fucking squares suck. Soon I will amke sure you can only have round shit. I tried to impress a bitch with a fucking square once, wanna know what the fuck happened? She fucking cried! Cried so loud, even saying, "A trapezoid would have been better!" The nerve of that bitch.

The nerve of /math/. Someone here PROMISED that the bitch would let me stick my shit in her if I gave her a square. You owe me a fixed marriage./ Send nudes of your daughter, I call it even.
George Banderwater - Sat, 07 May 2016 05:04:23 EST ID:A2j/BW/W No.15113 Ignore Report Quick Reply
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You're a square!

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