Fourier Cosine series of cos(x)

[Sarahisme]

Hello peoples,

 

I think this is a trick question... well sort of

 

 

for part (a) i get that the cosine Fourier Series for f(x) = cos(x) to be:

 

 

i hope that is ok, but its part (b) that is troubling me...

 

is all that happens as is that the cosine Fourier series of cos(x) goes to 0?

 

i am guessing i am missing some trick to this question?

 

Cheers!

 

Sarah

[Sarahisme]

its cool, got it! don't worry guys