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IMO 2017 — Complete Shortlist Question 17

IMO Shortlist · IMO 2017 — Complete Shortlist

Question 17

Let $A B C D E$ be a convex pentagon such that $A B=B C=C D, \angle E A B=\angle B C D$, and $\angle E D C=\angle C B A$. Prove that the perpendicular line from $E$ to $B C$ and the line segments $A C$ and $B D$ are concurrent.