List of top Signals and Systems Questions on Operation on Signals

Let \(x_1(t)=\cos(2\pi nt)\) and \(x_2(t)=2\sin(4\pi nt)\) represent two sinusoids for a positive integer \(n\) and \(-\infty<t<\infty\). Which of the following statements about \(x_1(t)\) and \(x_2(t)\) is/are valid?