Question 95
A line $g$ intersects a circle $k$ at $A,B$. The perpendicular bisector of $AB$ intersects $k$ at $C,D$. Let $P$ be another point on $g$, outside $k$. The parallels through $P$ to $CA,CB$ meet the lines $CB,CA$ at $X,Y$, respectively. Prove that $XY\perp PD$.