Short Program: Fourier Series Expansion on Matlab, PLEASE HELPP!!!

A square wave of period 2L is a step function which is equal to 1 for x from 0 to L, then is equal to -1 for x from L to 2L.

A square wave can be approximated by this Fourier Series expansion:

infinity

f(x )=(4/pi) ?((1/n)sin(npix/L))

n=1,3,5....

I need to write a program that prompts the user for a maximum value for n and a value for L.

Using those values, I have to compute the Fourier Series expansion for a square wave and plot the result.

L must be a positive number, and n must be a positive odd integer.

If the user does not provide an acceptable number, you should detect the error, display an error message, and stop your script.

You should evaluate the function for 500 values of x, evenly distributed from 0 to 2L.

If someone could please help me with this, that would be great because I don't even know how to start off writing the script for this program.