Answer
The angle of the sun is $~~72^{\circ}$
Work Step by Step
As the shadow moves up the wall, $\frac{\Delta y}{\Delta x} = tan~\theta$
Let $v_y$ be the speed of the shadow up the wall.
Let $v_x$ be the speed of the hawk.
Then:
$tan~\theta = \frac{v_y}{v_x}$
$\theta = tan^{-1}~(\frac{v_y}{v_x})$
$\theta = tan^{-1}~(\frac{45~m/s}{15~m/s})$
$\theta = 72^{\circ}$
The angle of the sun is $~~72^{\circ}$
