Mechanics question - centre of mass?

Question

Hi, could you help me with this question and also explain the steps, thanks!

A uniform semicircular lamina is suspended from an end point of its diameter. Assuming that it hangs freely under gravity, calculate in radians the angle between the diameter and the vertical.

Answer 1

Answer: α =
arctan (V(sphere)/[πS(circle)]) =
arctan (4/(3π)) =
0.401373501979140242516196351461