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


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- Wed, 08 Jun 2016 18:56:24 EST 3U6ZTH6i No.15153
File: 1465426584120.gif -(333697B / 325.88KB, 256x256) Thumbnail displayed, click image for full size. Mathemusings
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.

If so, how does the flat A# come about?
Hugh Sessledock - Thu, 09 Jun 2016 03:14:56 EST lYjTKStM No.15154 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 3U6ZTH6i No.15155 Reply
1465468421138.jpg -(25519B / 24.92KB, 1304x617) Thumbnail displayed, click image for full size.
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 3U6ZTH6i No.15164 Reply
1465937184594.jpg -(13970B / 13.64KB, 394x467) Thumbnail displayed, click image for full size.
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

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- Fri, 03 Jun 2016 05:39:35 EST FvfJV3ZM No.15146
File: 1464946775420.png -(17720B / 17.30KB, 682x185) Thumbnail displayed, click image for full size. Generating Polynomial
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 A2j/BW/W No.15147 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.


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- Sun, 29 May 2016 19:59:52 EST lgvPZ+E8 No.15140
File: 1464566392861.jpg -(94901B / 92.68KB, 650x434) Thumbnail displayed, click image for full size. Probability
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 lYjTKStM No.15141 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.
Eliza Crabblewater - Mon, 30 May 2016 21:48:39 EST lgvPZ+E8 No.15143 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

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

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- Sat, 07 May 2016 01:20:21 EST HaG6KVm7 No.15112
File: 1462598421690.png -(847B / 847bytes, 225x225) Thumbnail displayed, click image for full size. Fuck squares
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 A2j/BW/W No.15113 Reply
1462611863500.jpg -(440782B / 430.45KB, 960x540) Thumbnail displayed, click image for full size.
You're a square!

What type of math are you studying?

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- Sun, 14 Feb 2016 19:31:46 EST Dk8yywxc No.15046
File: 1455496306932.jpg -(396464B / 387.17KB, 2480x3508) Thumbnail displayed, click image for full size. What type of math are you studying?
Right now I'm studying large cardinals in set theory and trying to learn more about algebraic topology. A good place to start with topology is the "Topology" by Munkres, and if you have a strong set-theoretic back ground I recommend "The Higher Infinite" by Kanamori for learning about large cardinals. The fact that the existence of a large enough number can be equivalent to something that has nothing to do with cardinals at face value still fascinates me. Here's an interesting chart that shows how we can assume the existence of large enough cardinals right up to contradiction.

What parts of math are you interested in or studying? Why? What are some resources that you recommend for others to get into it?
1 posts omitted. Click View Thread to read.
Hugh Drubberforth - Thu, 31 Mar 2016 20:52:08 EST fIwfJdEz No.15078 Reply
I'm working through abstract algebra. I've got an engineering degree, but the math we learn there is much more pragmatic, model-oriented, and number-focused. Whereas math like this, in and of itself, is a bit like a model. For example I personally conceptualize mappings as a sort of data-typing, that's just where it rests in my mind, but I know that it is a more general concept than that-- allowing quotient sets and such has sort of blown my mind in this regard.

I'm trying desperately to cling on to Allan Clark's Abstract Algebra book, which I've been told is really not for beginners. I can see that, but I can fill in the gaps with stuff on the internet. I spend a lot more time puzzling about this book than with other intro texts. Fiddling with the numbers, and trying hard to convince myself of things, and solve problems with my own reasoning, instead of regurgitating the examples.

It's pretty fuckin' rough so far, especially since the only work I have with formal logic/sets is a brief introduction in engineering statistics, and in "severely boiled the fuck down" discrete math 301. And that was about 10 years ago, so yeah. But I'm trying, and I can usually understand the proofs others arrive at, if not nearly arrive at them myself. I'm probably wasting my time, but I like the puzzles.
Hannah Dinningtitch - Sat, 09 Apr 2016 18:19:26 EST LR+0MgV1 No.15085 Reply
1460240366149.png -(258528B / 252.47KB, 1920x1080) Thumbnail displayed, click image for full size.
I like to study computational theory, so things like lambda calculus and functional programming langues. It's a really nice mix between pure mathematics and computer science.
Hannah Sollernodge - Fri, 22 Apr 2016 12:45:25 EST WD6PkLOh No.15099 Reply
Well I studied Pharmacology, but I've been re-reading some of my Advanced Higher (stuff you do in the last year of secondary education) maths and reading a couple of books aimed at the average person. Are there any college-level maths topics which are particularly cool or satisfying? I loved that feeling of it all coming together when I relearned partial fractions, proofs, calculus (before you get trig functions involved and it all goes to shit). Anything in the same vein I could learn now? I have no problem putting in hours of work, and I usually don't have a problem grasping new mathematical concepts

i can't do math

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- Fri, 15 Apr 2016 18:21:07 EST YoFLr1Ak No.15092
File: 1460758867923.jpg -(272402B / 266.02KB, 1300x924) Thumbnail displayed, click image for full size. i can't do math
im 25 and i can barely understand algebra, im a high school drop out.

what am i going to do i need to go back to college but if i don't pass their math test i am not allowed in....what shall i do?
Samuel Drimbletedging - Wed, 20 Apr 2016 22:12:08 EST RHLOntyV No.15097 Reply
If you're going to community college you should be fine, many have pre-algebra remedial classes you can take.
Hannah Sollernodge - Fri, 22 Apr 2016 12:37:03 EST WD6PkLOh No.15098 Reply
I recommend Khan academy very highly. I'm an amateur but I really love maths, and I love to share it with my girlfriend (who never did well at school), but sometimes we just get stuck on something and I've explained it every way I can to her.
Without fail, we watch the KA video and she understands in 5 minutes


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- Fri, 15 Apr 2016 11:45:52 EST FXvLlomd No.15090
File: 1460735152003.png -(363794B / 355.27KB, 1920x1080) Thumbnail displayed, click image for full size. PDEs
guys help

Why are we assuming h(x, t) to be a fourier sine series instead of using the whole fourier series? It's certainly easier for decomposing the equation into an ordinary differential equation but what if it can't be represented by sine alone?

Also, why do we assume that the function in the integral from 0 to L of h(x, t)*sin(n*pi*x/L)dx is an even function? If it's an odd function, then the integral converges to zero and then what do you do?
Jenny Cabblehall - Fri, 15 Apr 2016 16:19:42 EST FXvLlomd No.15091 Reply
Ok so i understand now why h(x,,t) is a fourier sine series, but it seems like this method only works for when h(x,t)'s x part is an odd function, otherwise the integral either becomes zero or the function has a sine AND cosine series representation. If this is the case, this method doesn't work, right?

I don't believe in Math

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- Thu, 07 Jan 2016 00:39:32 EST +mzdzIig No.15015
File: 1452145172589.jpg -(8086B / 7.90KB, 252x200) Thumbnail displayed, click image for full size. I don't believe in Math
how come you can't put any symbol in any order and make the claim that it is what you say it is?

>its a conspiracy
5 posts omitted. Click View Thread to read.
Molly Clayfield - Wed, 09 Mar 2016 02:29:30 EST FwRHmRUr No.15067 Reply
god invented math to troll you fucks, checkmate
Albert Fonderchork - Sun, 10 Apr 2016 14:19:31 EST BI41XwUF No.15087 Reply
1460312371052.jpg -(59771B / 58.37KB, 600x799) Thumbnail displayed, click image for full size.
Apart from the most elementary mathematics, like arithmetic or high school algebra, the symbols, formulas and words of mathematics have no meaning at all. The entire structure of pure mathematics is a monstrous swindle, simply a game, a reckless prank. You may well ask: "Are there no renegades to reveal the truth?" Yes, of course. But the facts are so incredible that no one takes them seriously. So the secret is in no danger.

How to become an amateur mathematician? Along with book recommendations.

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- Sat, 20 Sep 2014 20:13:43 EST aC7pKNlN No.14371
File: 1411258423261.jpg -(66533B / 64.97KB, 960x402) Thumbnail displayed, click image for full size. How to become an amateur mathematician?  Along with  book recommendations.
I have How to Solve it by Poyla, The Mathematical Experience , CRC Concise Encyclopedia of Mathematics, and Mathematical thought from Ancient to Modern Times.

Are there any good general mathematics books out there? I'm not too interested right now in becoming a mathematician that focuses on a very specific field.
2 posts and 1 images omitted. Click View Thread to read.
David Cebberwig - Mon, 22 Sep 2014 02:30:49 EST LZtslkSN No.14374 Reply
1411367449379.png -(11346B / 11.08KB, 152x79) Thumbnail displayed, click image for full size.
I am also an amateur mathematician. Pic related.
Cornelius Pendletedge - Mon, 22 Sep 2014 19:18:14 EST m9zbwPJj No.14377 Reply
1411427894409.jpg -(1493488B / 1.42MB, 1920x1200) Thumbnail displayed, click image for full size.

>Amateur as opposed to professional,
>I just want to learn math as a hobby.

That's not very helpful. Yes, I figured that by "amateur", part of what you meant is that you didn't expect to get paid for it.

Do you just want to amuse yourself? With easy problems? Hard problems? Do you want to publish?

Keep in mind that Pierre de Fermat was an amateur mathematician.


>and my background is a a few college algebra/Pre-calculus classes.

Then you should probably start with calculus. You can get a free calculus textbook here:


It'll make you say, "Damn, shit just got hyperreal."

The books you have aren't going to teach you much about actually doing mathematics (with the possible exception of the Polya book). You don't need to worry about overspecializing at this point. If your background is sophomore/junior year high school math*, you don't have a broad enough base to need to worry about overspecialization for quite some time.

*Yes, I know, you took college algebra. Which is the same algebra you do in high school, unless you're in remedial math.
Shit Brookford - Thu, 10 Mar 2016 22:12:27 EST Owidv0kC No.15068 Reply
1457665947160.jpg -(542974B / 530.25KB, 921x1300) Thumbnail displayed, click image for full size.
Start here => "Polya - How to Solve It"

So what would you do if...

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- Wed, 27 Jan 2016 06:47:23 EST 4TF5vVu6 No.15033
File: 1453895243617.jpg -(132162B / 129.06KB, 960x671) Thumbnail displayed, click image for full size. So what would you do if...
You had actually figured out how to quantify stupidity?

I don't mean an IQ test, I mean if you had spatial sequence synaesthesia and you could literally see the difference between stupid people and smart people, as well as translate it into a quantity and develop a comprehensive test for deriving exactly how fucking stupid someone was?

I am worried about either having my discovery stolen or being murdered by some letter soup agent. I feel like Ignaz Semmelweis. This is probably the last place I will look for help. Pic only slightly related in a very abstract sense.
1 posts and 1 images omitted. Click View Thread to read.
Fuck Craffingshit - Thu, 18 Feb 2016 15:44:54 EST lPEtDIQb No.15049 Reply
Gotta say, this sounds like utter nonsense (extraordinary claims need extraordinary evidence). If you think your methods are valid and you're worried about having your discovery stolen, then publish in a (reputable) journal. That's typically how this sort of thing is done.

If you are worried about alphabet soup agents, I'm afraid there's precious little you can do about that.
Molly Clayfield - Wed, 09 Mar 2016 02:18:38 EST FwRHmRUr No.15066 Reply
ordinary claims need ordinary evidence

Not certain synesthesia is anything more than 'normal' active imagination, some being more active than others' (from a lack of beatings, realistically.)

There's something similar where you can read someone's face and judge pretty accurately their experience before they speak, but there's usually other more obvious give-aways.

Doing better in one area of math compared to another

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- Sat, 05 Mar 2016 21:27:39 EST RHLOntyV No.15063
File: 1457231259567.jpg -(2159106B / 2.06MB, 4096x2535) Thumbnail displayed, click image for full size. Doing better in one area of math compared to another
Anyone have something similar happen to them?
for example, I'm taking both a college algebra and trig class this semester, and while both are fairly challenging, I don't do as well on college algebra tests compared to trig tests.
The trig class moves faster and the tests are more in-depth, I study the same amount for both classes, but I consistently score higher in trig. I think it's because there's more room for "stupid mistakes" in algebra, as most of it is pure arithmetic.
Any thoughts on this?
Augustus Brazzleleck - Sun, 06 Mar 2016 03:18:38 EST bxbjkBRo No.15064 Reply
Consider this. This is probably the fourth algebra class you've taken, whereas the trig class you're taking is your first introduction to the subject.

Your algebra class is relatively more advanced and more in depth. What's more, there isn't uniform difficulty across math courses. Don't worry about it, just study harder in algebra.
Nicholas Brisslewater - Sun, 06 Mar 2016 12:39:55 EST Dk8yywxc No.15065 Reply

Algebra is infamous for being tough for even very intelligent people. You want to try to learn methods, ways of looking at problems rather than memorizing a solution. It's easy to check step by step a solution that's done for you, but sometimes you have to stare at a problem until it is intuitive why it's solved that way. This is true for all levels of math.

Learn math from scratch

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- Wed, 24 Feb 2016 02:37:19 EST NaTojNkl No.15058
File: 1456299439874.jpg -(53753B / 52.49KB, 453x604) Thumbnail displayed, click image for full size. Learn math from scratch
My first semester at the university was fun, every day I smoke wead. But that is not I was supposed do, so now I have to learn all the stuff, from limits to integrals and from matrices to geometry. Can you suggest some cool books for me, guys?
And excuse my English.
Lillian Clayfoot - Tue, 01 Mar 2016 12:21:48 EST jM5wsKbL No.15062 Reply
1456852908437.jpg -(777835B / 759.60KB, 1024x768) Thumbnail displayed, click image for full size.
I had a calculus for dummies that was great.

protip: leave a spare hour after your math classes to work on your assignments while the knowledge is fresh, then you dont have to worry about as much homework.

also, be keen and go ask your prof questions. its their job and your respnsibility to ask when your confused

Unsolved Zodiac ciphers

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- Tue, 23 Feb 2016 23:40:50 EST edLsgdZo No.15057
File: 1456288850535.png -(278484B / 271.96KB, 475x642) Thumbnail displayed, click image for full size. Unsolved Zodiac ciphers
Has anyone taken a crack at this?
Esther Desslefure - Mon, 29 Feb 2016 12:42:19 EST J4OUpAxW No.15061 Reply
How do wewe even know thait's not meaningless gibberish, like thishttps://en.m.wikipedia.org/wiki/Voynich_manuscript

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