7.3. The frequency which, under the sampling theorem, must be exceeded by the sam- pling frequency is called the Nyquist rate. Determine the Nyquist rate corresponding to each of the following

signals: (a) x(t) = 1 + cos(2,000mt) + sin(4,000mt) (b) x(t)=sin(4,000) (c) x(t) = at sin(4,000) WI