KöMaL 2017 B4841

The circle $k$ centred at $O$ intersects line $e$ at points $A$ and $B$, and it intersects the perpendicular bisector of line segment $OB$ at points $C$ and $D$. Prove that the angle bisector of angle $COA \sphericalangle$ and line $e$ enclose an angle of 60 degrees.