
The time has come, and I have been politely asked to remove my math questions from the Big Programming Thread.
So why not have a math thread? Hopefully it isn't just me by myself in here, but I would think that there should be as much, if not more interest in maths than in programming anyways.
So what is welcome here? Anything math related! Random questions, theory, homework discussion, anything. But we must have proper etiquette (as arbitrarily determined by me with the following Dos and Don'ts.
Do: Be respectful  don't be condescending or make fun of people. Not everyone is at the same level and we should all be here to learn or teach. There will be zero tolerance for excessive rudeness or trolling.
Use google  If you are looking for help understanding or working out a problem, do a simple search to see if there are sufficient resources out there for you already. If it's a problem with many resources but you still don't understand, explain why.
Accurately explain your problem  if people are expected to put time into helping to explain a problem, then you should be putting the time in to accurately explain the problem so they can understand it.
Make your work readable. If you upload a scan/pdf, we need to be able to read the whole thing. If the equation is too complicated (symbols, sums, etc) to simply type out and you don't have a scanner, you can use latex online. There is a free editor: here.
Do not: Use this thread to cheat on homework. It's for learning. You don't learn by cheating. I don't think it's reasonably enforceable to try to stop people from cheating, but if people think you are only here for solutions then you will probably be shamed for it.
Take contributors for granted. Don't spam your questions, or get upset if you don't get answered. If you received help, maybe try to help others if you can. Or at least continue to be respectful.
Go off topic. If it's loosely related to math you can probably get away with it. If it's completely off topic you may lose privileges to post in here.

I've been eager to learn about Fourier transform. In particular I wanted to use it to do pitch adjustments of sound samples. I have some code here for playing sounds, and want to add some pitch adjustment stuff.
Would anyone mind chatting with me about the mathematics? I was hoping to find someone knowledge about Fourier transforms and their applications that I could bounce a bunch of questions off of. Please PM me if anyone would be so kind!
Edit: Ended up figuring it all out! Posted followup on 6th page of this thread here.

i took a 3rd year math course in "applied combinatorics". 4 month course. had to take it to complete my degree. the grade was based on 2 midterms at 25% each and the final exam at 50%.
i got the 3rd highest mark in a class of ~35 in the 1st midterm with 50/100. 1 guy got 66/100 and another guy got perfect, 100/100. obviously the class we get our grades back we're a little devastated.... lots of moaning whining and complaining... prof speaks up.... and says...
"if i flip a coin 35 times and it only comes up heads 2 times i do not statistically adjust that result. i note it as a special and unusual case". what he was saying was "there could well be 33 morons in this room ... so shut up you idiots"
a bunch of people dropped the course without academic penalty immediately after receiving their grade in the 1st midterm. There were 20 people left in the class. it was fucking brutal. toughest math course i ever took. i spent 10 amazing fun filled weekends with my applied combinatorics textbook that semester. i still remember half the content of the course and i took it more than 8 years ago.

@JimmyJRaynor: if your university needs more than 3/35 people to pass the year (and it's very likely), your course was very badly designed imho :o.
I have a question but I'm not sure if the answer is trivial or if we don't have the answer yet; it's related to probability altho with some CS in it so I'll ask there!
Say we build a bayesian model that estimates the odds of a real life event A happening at 95%. But the event happens in real life only once (the results of an election for example). Says A happens as "predicted". So what? Was our estimation accurate? Maybe it actually had 80% chances of happening, but it still happened because it's still a likely event. But it didn't necessarily happen by random chance, especially if the event we are trying to predict is an election and not some randomly generated thing. Thus how can we judge if our model was well suited? I guess if we just want to have our model predict what will happen while minimizing loss and so on, like we often do, then there is no problem. But I feel like there an inherent philosophical/epistemological problem with Bayesian models :/. edit: would us be able to reproduce the event results enough times for it to be statistically significant, allow us to correctly evaluate if our estimation was right? But it still wouldn't be an absolutely precise estimation, and is it even possible to have such a thing?
(think about FiveThirtyEight and the likes for context)
edit 2 : another "application" of this question would be with smartphones weather predictions! They probably use some kind of bayesian model for that, and they will tell you: "there is 30% chances that it'll rain at this hour." how are we supposed to use this information? Assuming their estimation is roughly correct, a wise choice would be to take an umbrella if doing so is the result of a positive mathematical expectation, because we have the probability of the event... but how can I quantitatively assess how not having an umbrella would be a pain in the ass? Like I can say: "I would feel neutral if I have an umbrella and it is raining, so I assess 0 value to having an umbrella". But to have a rough idea of how painful it'll be not having an umbrella if it happens to rain... I would need to know how much and for how long it would rain! But if they can't say that to us, I can't really put their intel about the weather to good use. It won't ever be the wisest choice :/.

I fixed your thread title case. Also, if you want any specific rules set in a mod note, let me know.
Also, it's super awesome to have created a thread that got so large and diverse it had a baby ♥


On June 09 2017 11:11 Nin54545 wrote:Who is able to resolve this ? http://imgur.com/a/xmf9fThis should be very difficult...
Any program such as Mathematica or Matlab will give you answer ezpz. Why bother calculating it by hand?

On June 09 2017 11:27 Lebesgue wrote:Any program such as Mathematica or Matlab will give you answer ezpz. Why bother calculating it by hand? It would take a very long time to properly type in the right order so it is probably safer to quickly check if it's solvable (by looking for forbidden operations or whatever), and if it is indeed a lot of software could do it.

On June 09 2017 11:11 Nin54545 wrote:Who is able to resolve this ? http://imgur.com/a/xmf9fThis should be very difficult...
With a basic (high school) understanding of logarithms and trigonometry, this should be a cinch conceptually. It's just a lot of procedures and arithmetic.


On June 09 2017 11:11 Nin54545 wrote:Who is able to resolve this ? http://imgur.com/a/xmf9fThis should be very difficult... Seems trivial, actually. Just a load of simplifications and then arithmetic. But things like the sqrt of a cubed number are simply the absolute value of that number. I looked it over and don't see an obvious multiplication by 0, so don't feel like doing the work. But it's not difficult as such.

On June 09 2017 16:07 Acrofales wrote:Seems trivial, actually. Just a load of simplifications and then arithmetic. But things like the sqrt of a cubed number are simply the absolute value of that number. I looked it over and don't see an obvious multiplication by 0, so don't feel like doing the work. But it's not difficult as such.
Oh... ok...

On June 09 2017 13:01 DarkPlasmaBall wrote:With a basic (high school) understanding of logarithms and trigonometry, this should be a cinch conceptually. It's just a lot of procedures and arithmetic.
Lot of procedures ? 1/2 hours ?

On June 09 2017 11:32 Poopi wrote:Show nested quote +On June 09 2017 11:27 Lebesgue wrote:On June 09 2017 11:11 Nin54545 wrote:Who is able to resolve this ? http://imgur.com/a/xmf9fThis should be very difficult... Any program such as Mathematica or Matlab will give you answer ezpz. Why bother calculating it by hand? It would take a very long time to properly type in the right order so it is probably safer to quickly check if it's solvable (by looking for forbidden operations or whatever), and if it is indeed a lot of software could do it.
thanks man

On June 09 2017 11:09 tofucake wrote: I fixed your thread title case. Also, if you want any specific rules set in a mod note, let me know.
Also, it's super awesome to have created a thread that got so large and diverse it had a baby ♥
And a big baby to boot

On June 09 2017 18:04 Nin54545 wrote:Show nested quote +On June 09 2017 13:01 DarkPlasmaBall wrote:On June 09 2017 11:11 Nin54545 wrote:Who is able to resolve this ? http://imgur.com/a/xmf9fThis should be very difficult... With a basic (high school) understanding of logarithms and trigonometry, this should be a cinch conceptually. It's just a lot of procedures and arithmetic. Lot of procedures ? 1/2 hours ?
Probably about 35 minutes if you have a calculator and know what you're doing.

On June 09 2017 18:04 Nin54545 wrote:Show nested quote +On June 09 2017 13:01 DarkPlasmaBall wrote:On June 09 2017 11:11 Nin54545 wrote:Who is able to resolve this ? http://imgur.com/a/xmf9fThis should be very difficult... With a basic (high school) understanding of logarithms and trigonometry, this should be a cinch conceptually. It's just a lot of procedures and arithmetic. Lot of procedures ? 1/2 hours ? You can just use a calculator. Don't be scared by complex looking things. Take a step back and look at what is actually written. In the end it's just a sum and multiplication of a few terms.
Now all you have to do is calculate A till E first and then use the sum for the final answer.


I updated the OP. If you upload scans, please make sure they are readable.
If your problems are too hard to simply type and you do not have a scanner, please use latex. An easy solution is an online latex editor like this: https://www.codecogs.com/latex/eqneditor.php

On June 09 2017 20:12 travis wrote:I updated the OP. If you upload scans, please make sure they are readable. If your problems are too hard to simply type and you do not have a scanner, please use latex. An easy solution is an online latex editor like this: https://www.codecogs.com/latex/eqneditor.php
Good advice.
Here's A done for you all
\dfrac{\log_{100}(10)}{\dfrac{1}{100}}



