# Fourier Series. Writing a partial sum as an integral.

1. Mar 12, 2013

### Popinfresh

1. The problem statement, all variables and given/known data

Given: View attachment 56653 , show that this can be written as: View attachment 56651 .

2. Relevant equations

Hint: View attachment 56652

3. The attempt at a solution

Quite confused by this question. For f'N I have:

$\frac{4}{∏}$Ʃ$\frac{cos((2n -1)x)}{(2n - 1)^{2}}$ but i'm not sure where to go from here.

I have read about the Dirichlet kernel, which is what I think I require, but I am rather lost.

Any help is appreciated.

Cheers.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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