- #1

Niles

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**[SOLVED] Fourier series**

## Homework Statement

Hi.

Please take a look at:

https://www.physicsforums.com/showthread.php?t=104306

It is part 1 (finding the Fourier-series for f(x) = |x|) I am having trouble with.

## The Attempt at a Solution

Ok, I can write f(x) = |x| for -pi =< x < pi as:

f(x) = x for 0 =< x < pi and

f(x) = -x for -pi =< x =< 0.

The function has period T=2.

I want to find a_n = int[f(x)*cos(n*pi*x)]dx with limits -1 .. 1. I split this integral up in two:

a_0 = int[-x}dx + ... but what are the limits? Are they -pi..0 or -1..0? The way I see it, neither of the limits work since a_0 must be pi.

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