# Thread: is this a sine or cosine fourier series...

1. ## is this a sine or cosine fourier series...

is this a sine or cosine fourier series...

f(x) = { sin^2 (2x) -pi < x < pi

2. Originally Posted by llinocoe
is this a sine or cosine fourier series...

f(x) = { sin^2 (2x) -pi < x < pi
Well you are taking the sine, squaring it, and doubling its frequency. When you square it, you make all the negative values positive, and doubling the frequency has no effect on the evenness/oddness.

So it is an even function now. And even function has only cosine terms.