MathDB
Angle PDE

Source: Serbia MO 2018 P1

April 2, 2018
geometryincentermoving pointsSerbiaTriangle

Problem Statement

Let ABC\triangle ABC be a triangle with incenter II. Points PP and QQ are chosen on segmets BIBI and CICI such that 2PAQ=BAC2\angle PAQ=\angle BAC. If DD is the touch point of incircle and side BCBC prove that PDQ=90\angle PDQ=90.