please show every step for each subproblem

$2\mathrm{.}5.$ Find the half$-$power beamwidth $($HPBW$)$ and first$-$null beamwidth $($FNBW$),$ in radians and degrees, for the following normalized radiation intensities:

$($a$)U()=coscos(2)$

$($b$)U()=co{s}^{2}co{s}^2(2)$

$($c$)U()=cos()cos(3)$

$($d$)U()=co{s}^2()co{s}^2(3)$

$($e$)U()=cos(2)cos(3)$

$($f$)U()=co{s}^2(2)co{s}^2(3)$