Exponential Fourier Series for Pulse Train

[opticaltempest]

Homework Statement

I need help finding the exponential Fourier series for the pulse train below.

http://img329.imageshack.us/img329/1184/20080427091409ev5.jpg

Homework Equations

p_T(t)=\sum_{n=-\infty}^{\infty}{D_n e^{j2nt}

D_n=\frac{1}{T_0}\int_{T_0}^{}{x(t)e^{-j2nt}dt}

The Attempt at a Solution

http://img74.imageshack.us/img74/2376/20080427093457iy6.jpg

I know that D0=0.2. However, I cannot evaluate my final answer for n=0 because I have n in the denominator. Where am I going wrong?

 

[quadraphonics]

The first line in your attempted solution has an error: you need to either include x(t) inside the integral, or change the limits of integration.

 

[opticaltempest]

I forgot to label on the graph that the magnitude of pt(t) is 1. Why can't I integrate from 0 to 0.4x10^-3 and multiply by 2 since there is even symmetry?