IMO 2011 Shortlist G7
Let ABCDEF be a convex hexagon all of whose sides are tangent to a circle ω with center O. Suppose that the circumcircle...
Category: Geometry
Problem
Let ABCDEF be a convex hexagon all of whose sides are tangent to a circle ω with center O. Suppose that the circumcircle of triangle ACE is concentric with ω. Let J be the foot of the perpendicular from B to CD. Suppose that the perpendicular from B to DF intersects the line EO at a point K. Let L be the foot of the perpendicular from K to DE. Prove that DJ = DL.