# Homework Help: Simple Fourier series problem

1. Mar 17, 2010

### springo

1. The problem statement, all variables and given/known data
Find the Fourier series for ex for x in (-1,1).
Find the Parseval identity.

2. Relevant equations

3. The attempt at a solution
$$c_{n}=\frac{1}{2}\int_{-1}^{1}e^{x}e^{-i n x}dx$$
Where cn are the coefficients of the Fourier series.

I tried plotting
$$\sum_{k=-\infty}^{\infty}c_{n}e^{i n x}$$
together with ex and it doesn't seem to be correct...

Thank you for your help!

Last edited: Mar 17, 2010
2. Mar 17, 2010

### LCKurtz

For starters, your formula for cn is wrong. For period P = 2p:

$$c_n = \frac 1 {2p}\int_{-p}^p f(x) e^{\frac {i n \pi}{p}}dx$$

In your problem p = 1.

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