Question 145
Let $\triangle ABC$ be a triangle. The points $D$ and $E$ lie on the sides $AC$ and $AB$, respectively. Bisector of angle $B$ intersect side $AC$ at a point $P$ and bisector of $\angle ADE$ intersect side $AB$ at a point $Q$. If $BP$ perpendicular to $DQ$, then prove that $PQ \parallel EC$.