10. (20 points) From a point outside the parabola $y^{2}=2 p x(p>0)$, draw two tangent lines $P A, P B$ to the parabola, with points of tangency at $A, B$ respectively. Let the circumcenter of $\triangle P A B$ be $Q$, and $Q$ does not coincide with the focus $F$ of the parabola. Try to find $\angle P F Q$.