MathDB
Angle Bisector at intersection of circumcircles

Source: Netherlands IMO TST 2019 P2

March 30, 2019
geometryangle bisectorcircumcircle

Problem Statement

Let ΔABC\Delta ABC be a triangle with an inscribed circle centered at II. The line perpendicular to AIAI at II intersects (ABC)\odot (ABC) at P,QP,Q such that, PP lies closer to BB than CC. Let (BIP)(CIQ)=S\odot (BIP) \cap \odot (CIQ) =S. Prove that, SISI is the angle bisector of PSQ\angle PSQ