MathDB
BMO Shortlist 2021 G2

Source: BMO Shortlist 2021

May 8, 2022
Balkanshortlist2021geometrybisectorincircle

Problem Statement

Let II and OO be the incenter and the circumcenter of a triangle ABCABC, respectively, and let sas_a be the exterior bisector of angle BAC\angle BAC. The line through II perpendicular to IOIO meets the lines BCBC and sas_a at points PP and QQ, respectively. Prove that IQ=2IPIQ = 2IP.