MathDB
Shortlist 2017/G1

Source: Shortlist 2017

July 10, 2018
geometryIMO ShortlistpentagonInscribed circle

Problem Statement

Let ABCDEABCDE be a convex pentagon such that AB=BC=CDAB=BC=CD, ∠EAB=∠BCD\angle{EAB}=\angle{BCD}, and ∠EDC=∠CBA\angle{EDC}=\angle{CBA}. Prove that the perpendicular line from EE to BCBC and the line segments ACAC and BDBD are concurrent.
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