Answer
$\theta=42^{\circ}$
Work Step by Step
We know that
$sin\theta=\frac{v}{v_s}$
where $v$ is the speed of sound which is given as $331\frac{m}{s}$ that is equal to 1 Mach. Whereas $v_s$ is the speed of the aircraft given as 1.5 Mach.
Putting the values, we get
$sin\theta=\frac{1}{1.5}=0.66$
$\theta=sin^{-1}(0.66)$
$\theta=41.8^{\circ}=42^{\circ}$
$\theta=42^{\circ}$
