Originally Posted by

**NFS1** Hi,

Im trying to attempt a few questions for an exam in a couple of weeks, but am finding it hard, so was wondering if anyone on here is able to help. Below is the question:

1. The function *f(x)* is periodic with period and is defined by

f(x) = {-cos x when -pi <x<0

{cos x when 0<x<pi

a) Sketch *f *from x=-3pi to x=3pi .

b) Decide if f is an even, odd function or neither.

c) Find the Fourier series of *f.*

d) By choosing a suitable value of x sum the series

1/1.3 - 3/5.7 + 5/9.11 - 7/13.15 + .........