A certain antenna has a radiation intensity given by

\[
F(\theta, \phi)=\left\{\begin{array}{ll}
\left|\cos ^{n} \thetaight| & 0 \leq \theta \leq(\pi / 2) \\
0 & (\pi / 2) \leq \theta \leq \pi
\end{array}ight\}
\]

Compute the directivity for \(n=1,2\).