Question 81
Consider a regular prism $ABCA'B'C'$. A plane $\alpha$ containing point $A$ meets the rays $BB'$ and $CC'$ at points $E$ and $F$ such that
$$
\text{area } [ABE] + \text{area } [ACF] = \text{area } [AEF].
$$
Find the angle determined by the planes $AEF$ and $BCC'$.
$$
\text{area } [ABE] + \text{area } [ACF] = \text{area } [AEF].
$$
Find the angle determined by the planes $AEF$ and $BCC'$.