Answer
$0.97^{\circ}$
Work Step by Step
We can use the given diameter of the antenna, $d=2.3m$, and wavelength, $\lambda=1.6*10^{-2}m$ in equation (36-12), to find the angle, $\theta$.
$\sin \theta= 1.22 \frac{\lambda}{d}$
$ \theta=\arcsin( 1.22 \frac{\lambda}{d})$
$ \theta=\arcsin( 1.22 \frac{1.6*10^{-2}m}{2.3m})$
$\theta = 0.487^{\circ}$
Since we are required to find the angular width, $2\theta$;
$2\theta=2*0 .487^{\circ}=0.97^{\circ}$
