# sketching frequency domain representation

I've been given this signal and asked to sketch a frequency domain representation how do i do that? how do you know which frequency components are present in the signal?

• In other words: the signal has the form $\cos(A)\cos(B)$, which is equal to $\cos(A+B)+\cos(A-B)$ (ignoring a scale factor). – MBaz May 24 '16 at 1:01