IMO 2021 Shortlist G8
Letω bethecircumcircleofatriangleABC,andletΩA beitsexcirclewhichistangent to the segment BC. Let X and Y be the intersec...
Category: Geometry
Problem
Letω bethecircumcircleofatriangleABC,andletΩA beitsexcirclewhichistangent to the segment BC. Let X and Y be the intersection points of ω and ΩA. Let P and Q be the projections of A onto the tangent lines to ΩA at X and Y , respectively. The tangent line at P to the circumcircle of the triangle APX intersects the tangent line at Q to the circumcircle of the triangle AQY at a point R. Prove that AR KBC. 10 Saint-Petersburg — Russia, 16th–24th July 2021