Question 153
Let $ABC$ be a scalene triangle and $F$ be midpoint of arc $BC$ of circumcircle of triangle $ABC$ containing $A$. The circle passing through $A$ and $F$ intersected to the rays $[BA]$ and $[CA]$ at $M$ and $N$, respectively. Let $P$ be intersection of $MC$ and $NB$. Let $S$ be the point such that the quadrilateral $ABSC$ is a parallelogram. Prove that $\angle BSP = \angle CSP$.