Question 95
Let $k$ be a semicircle with diameter $PQ$. Consider a chord $BC$ of fixed length $d$ whose endpoints are distinct from $P$, $Q$. A ray of light emanating from $B$ reaches point $C$ after reflecting from $PQ$ at such a point $A$ that $\angle PAB = \angle QAC$. Prove that $\angle BAC$ doesn't depend on the position of the chord $BC$ on $k$.
(Šárka Gergelitsová)
(Šárka Gergelitsová)