TR-MO 2001 Problem 5

Two nonperpendicular lines throught the point $A$ and a point $F$ on one of these lines different from $A$ are given. Let $P_{G}$ be the intersection point of tangent lines at $G$ and $F$ to the circle through the point $A$ , $F$ and $G$ where $G$ is a point on the given line different from the line $FA$ . What is the locus of $P_{G}$ as $G$ varies.