$7\mathrm{.}3.$ 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:

$($b$)$ x$($t$)=$ sin$(4,0007$Tt$)$

$7$Tt

$($c$)$ x$($t$)=($ sin$(4,$~~$0$m$)$ t