A waveform v(t) has a Fourier transform which extends over the range -F to +F in the frequency domain. The square of the waveform v(t), that is, v(t) v(t), then has a Fourier transforms which extends over the range:
a) -F to +F
b) -2F to +2F
c) -3F to +3F
d) -4F to +4F
The solution involves an explanation of the frequency domain of a waveform with a Fourier transform.