IMO Shortlist 2007 problem G8
Kvaliteta:
Avg: 4,0Težina:
Avg: 9,0 Point lies on side of a convex quadrilateral . Let be the incircle of triangle , and let be its incenter. Suppose that is tangent to the incircles of triangles and at points and , respectively. Let lines and meet at , and let lines and meet at . Prove that points , , and are collinear.
Author: Waldemar Pompe, Poland
Author: Waldemar Pompe, Poland
Izvor: Međunarodna matematička olimpijada, shortlist 2007