HMMT November 2019 T6

Let $A B C D$ be an isosceles trapezoid with $A B=1, B C=D A=5, C D=7$. Let $P$ be the intersection of diagonals $A C$ and $B D$, and let $Q$ be the foot of the altitude from $D$ to $B C$. Let $P Q$ intersect $A B$ at R. Compute $\sin \angle R P D$.