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

## Homework Statement

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

## Homework Equations

Hint: View attachment 56652

## 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.

## The Attempt at a Solution

#### Attachments

• hint.png
4.8 KB · Views: 371
• integral.png
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• partial sum.png
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