# Thread: Hexus.Help.Maths-Coursework :p (Fourier Series)

1. ## Hexus.Help.Maths-Coursework :p (Fourier Series)

Anyhting that involves Fourier is gay. Everyone knows this. But...

Compute the Fourier series representation of

f(x) = exp(ax), -pi <= x < pi.
Got the a0 term:

(sinh(a*pi))/(a*pi)

For an and bn i just keep going roun in circles for the integration by parts and splitting it up with different limits, evena nd odd functions etc isnt helping Any ideas?  Reply With Quote

2. If I understood what that meant, I'd help. But I dont, so i suggest teh following:

Click Here   Reply With Quote

3. Cheer for the useful replies Still as clueless as i was before tbh.  Reply With Quote

4. Ok..well its to do with the exponential trig identities.
(im an engineer so j is imaginary...learn to cope with it )

cos(nx) = { exp(jnx) + exp(-jnx) } / 2
and equivalent for sin,
and
exp(pi*j) = -1
(and exp(-pi*j) = 1)

but still i just get a mass of crap and i dont really know how to simplify it...

MATHS IS OFFICIALLY TEH GAY!!!!1111  Reply With Quote

5. all that says is cos(pi*i) = 0, which im not sure is true anyway.
what you actually mean is the integral -pi to pi is 0, whcih is not the same  Reply With Quote

6. writing it out, its not that difficult an integration, use the exponential identites, multiply by your initially function (rembering that exp(ax)*exp(bx) = exp((a+b)x) and it really isnt that difficult to integrate.  Reply With Quote

7. Originally Posted by herulach
all that says is cos(pi*i) = 0, which im not sure is true anyway.
Where did you get that from? stupid maths person  what you actually mean is the integral -pi to pi is 0, whcih is not the same
...?
What?
integral of what? integral of sin is 0 yeah...as is cos...

its not the integration part that screws me over...its once you have done that, put in the limits...simplifying it seems to be beyond me   Reply With Quote