MathDB
Orthogonal projections and areas

Source: Polish MO

February 25, 2017
geometry

Problem Statement

In an acute triangle ABCABC the bisector of BAC\angle BAC crosses BCBC at DD. Points PP and QQ are orthogonal projections of DD on lines ABAB and ACAC. Prove that [APQ]=[BCQP][APQ]=[BCQP] if and only if the circumcenter of ABCABC lies on PQPQ.