Question 103
Let $A$, $B$, $C$ be three points on a circle of centre $O$. The perpendicular line from $O$ to $BC$ intersects line $AC$ at $P$, and the perpendicular line from $O$ to $AC$ intersects line $BC$ at $Q$. Let $L$ be the midpoint of $OC$ and $K$ the midpoint of $PQ$.
Prove that $KL$ is perpendicular on $AB$.
Prove that $KL$ is perpendicular on $AB$.