# Solving the Fourier cosine series

• chwala
You could certainly do that, but it would be confusing to anyone reading your work. Also, it doesn't matter if you use f(x) or x^2 in the end result, as long as it's clear what you're referring to.

#### chwala

Gold Member
Homework Statement
Kindly see attached (just need clarification on highlighted part).
Relevant Equations
Fourier cosine series

My question is; is showing the highlighted step necessary? given the fact that ##\sin (nπ)=0##? My question is in general i.e when solving such questions do i have to bother with showing the highlighted part...

secondly,

Can i have ##f(x)## in place of ##x^2##? Generally, on problems to do with Fourier series- what is usually indicated is ##f(x)##... or it does not matter? yes, i know that ##f(x)=x^2##. My question is in reference to the general widely used notation on such problems.

Cheers.

chwala said:
My question is; is showing the highlighted step necessary? given the fact that sin⁡(nπ)=0? My question is in general i.e when solving such questions do i have to bother with showing the highlighted part...
Yes, it's necessary, IMO. Otherwise, the transition from the line above the highlighted line to the one below it would be harder to follow. Several people have made comments in some of your threads that it was difficult to follow your work because of omitted steps.
chwala said:
Can i have f(x) in place of ##x^2##?
Why would you want to? Since you're finding the Fourier series of ##x^2##, why hide this fact by calling it f(x)?

WWGD, SammyS and chwala