Planetarion Forums - Maths people

Nodrog · 4 Jan 2003, 06:25

Except the obvious geometric uses. I was just reading something about probability in coin-tossing, and one of the formulas used to calculate the odds of a certain amount of heads occuring under certain conditions involved the use of Pi (Stringers forumla). A footnote said that "the use of pi may seem unusual since the problem has nothing to do with circles, but pi is one of those numbers that pops up all over the place in mathematics". I did not know this, and I am interested - where else does it 'pop up'?

4 Jan 2003, 06:29

Quote:

Originally posted by Nodrog
where else does it 'pop up'?

The crotch region of my trousers when i watch "Dark Angel".

Aryn · 4 Jan 2003, 06:46

Pi is the second letter in my sorority's name (Alpha Pi Beta)

but that doesn't really help you now does it :\

Aryn · 4 Jan 2003, 07:02

pav you just can't seem to get over this obsession with me.
you have this need to reply after i post something.. please stop.
it's just not possible for us. i mean.. you're over there, and i'm over here. well that and i'm already with someone else. you understand right?
sorry.

4 Jan 2003, 07:46

Quote:

Originally posted by Pavil Twice.
ever heard of canadian humour?

neither have canadians.

I saw that joke coming from before i even opened this thread to read your reply.

Auro · 4 Jan 2003, 08:07

Pi IS EXACTLY 3!

Ok, now that I've got your attention.....

I don't know.

Mirai · 4 Jan 2003, 08:49

pi pops up quite a bit in Trigonometry.

queball · 4 Jan 2003, 09:55

It's also used to donate a product,
b
Πx_i
i=a

and for π(n), the number of primes <= n

Mirai · 4 Jan 2003, 10:20

Quote:

Originally posted by Pavil Twice.
its not called trigonometry anymore, it is called Algebra.

no, that's a different math subject.

'|'empest · 4 Jan 2003, 10:34

i remember flicking through a prospectus in september (brum i think) for maths, it had examples of all these insane equations that all came out in the end as pi/4

apart from that, havn't got a pigging clue

menth0l · 4 Jan 2003, 10:51

Erm. Pi did pop up in my Linear Algebra class a few times but even then it was about radians and angles. So trigonometry basically.

4 Jan 2003, 11:15

Pi is used (atleast) in:

-anything involving circles,like area or spinning volumes
-Fourier Transformations (Transferring time based functions to frequency and back)
-Z-transformations (similar to Fourier, but don´t remember details)
-a bit in imaginary numbers (Eulers formula ?)
-(Pseudo)random number generation (computers)
-Statistical math
-filthering (DSP, basicly FFT)

Few uses I can think of...
Hope that helps.

menth0l · 4 Jan 2003, 11:20

googled

deerbarn · 4 Jan 2003, 11:20

a bloke in a bath tub

Ste · 4 Jan 2003, 13:03

Quote:

Originally posted by Pavil Twice.
who discovered pi.
and how?

Some ancient Greek i think discovered Pi...

In a circle - Pi*diameter = Circumference
- Pi*Radius^2 = Area
etc...
These are basically derived from the fact that in a segment of a circle the length of the circumference is angle(in radians)*radius there are 2pi radians in a circle.
Other than that - I dunno!
Another interesting 'number' is e. It's not that difficult to find though - A decent computer program could find it very easily...

Structural Integrity · 4 Jan 2003, 13:25

Quote:

Originally posted by Three_Eyes_Open
Making Odd films.

yes, I saw that one.... 't was really bizarre.

Anyway, I never heard of PI being used in statistics. However, since the numbers of PI are random (no one has ever managed to find a patern) I guess it could be used to calculate the chance of throwing coins, which is also a random something.

queball · 4 Jan 2003, 13:33

Quote:

Originally posted by Nodrog
Except the obvious geometric uses. I was just reading something about probability in coin-tossing, and one of the formulas used to calculate the odds of a certain amount of heads occuring under certain conditions involved the use of Pi (Stringers forumla).

There is no such thing as Stringers forumla! Nodrog is "stringing" you along!

Flayer · 4 Jan 2003, 14:51

after minutes of thoughts, i came to the conclusion that pi is infinitive because a circle is infinitive round, is this right?

4 Jan 2003, 15:04

acropolis · 4 Jan 2003, 16:15

Quote:

Originally posted by Demon1411
Pi is used (atleast) in:

-anything involving circles,like area or spinning volumes
-Fourier Transformations (Transferring time based functions to frequency and back)
-Z-transformations (similar to Fourier, but don´t remember details)
-a bit in imaginary numbers (Eulers formula ?)
-(Pseudo)random number generation (computers)
-Statistical math
-filthering (DSP, basicly FFT)

Few uses I can think of...
Hope that helps.

items 2,3, and 7 are kinder the same:/

But yeah mostly.

i'd say as follows
all geometry

all probability (another fun example: drop a 1' pin on a grid of squares 2' to a side. whats the probability the pin crosses a side of one of the squares? lo pi.)

all algebra (at least once you get to complex variables. pretty much everything makes sense once you know why e^(i*pi) = -1)

all number theory (some of the series that lead to pi: 1-1/3+1/5-1/7+1/9-...= pi/4 and 1 + 1/(2^2) + 1/(3^2) + 1/(4^2) +... = pi^2 / 6, and 1+ 1/(2^4) + 1/(3^4) + 1/(4^4) +... = (pi^4)/90. Solve the one with ^3 and you'll have your own page in math books from now until forever)

W · 4 Jan 2003, 17:24

2*Pi is the period of the trigonometric functions, which are used for complex numbers among other things. Also alternating series and stuff. PI doesn't really pop up that much for no reason, it's usually tied either to a periodic function or to complex numbers.

menth0l · 4 Jan 2003, 17:26

Quote:

Originally posted by Pavil Twice.
you see if we use google for everything on here then eventually we will use it for everything for both on and offline conversations.

imagine it.

standing at a bus stop and a little old lady turns to you and says 'when is the 17 due sonny?' to which you reply 'check google you piss stained old hag'

imagine it. go on.

It's a beautiful dream.

JonnyBGood · 4 Jan 2003, 17:30

Quote:

Originally posted by menth0l
It's a beautiful dream.

I still think you stole my ****ing idea for your rank.

PS What W said about trigonometric functions. Sine waves and alternating currents and other such equally pointless areas.

Nodrog · 4 Jan 2003, 23:03

Quote:

Originally posted by Demon1411

-Statistical math

This is the kind of thing I was after!

Could you give some examples? (preferably in the form of keywords that I can google for)

W · 4 Jan 2003, 23:11

Quote:

Originally posted by Nodrog
This is the kind of thing I was after!

Could you give some examples? (preferably in the form of keywords that I can google for)

Anything that can be rotated for instance, will involve pi. Like dropping a 5 cm match on a 5cm x 5cm grid of cells, the probability of the match landing on an edge will involve pi; not because any of the objects are round or periodic, but simply because the match can rotate.

This can happen more or less obviously in real life cases, and comming over PI is usually baffling to the discoverer, until he figures out why.

Ragnarak · 4 Jan 2003, 23:11

stirlings formula
binomial approximation
guassian distribution

etc

MrL_JaKiri · 4 Jan 2003, 23:46

Quote:

Originally posted by Demon1411
Eulers formula

Pi is only used in Euler's formula due to the presence of cos and sin; e^ix = cos x + i sin x, hence e^i(pi) = cos pi + i sin pi = -1.

Dead_Meat · 5 Jan 2003, 00:07

Pi theory explained