IMO Shortlist 2011 problem G5
Kvaliteta:
Avg: 0,0Težina:
Avg: 8,0 Let be a triangle with incentre and circumcircle . Let and be the second intersection points of with and , respectively. The chord meets at a point , and at a point . Let be the intersection point of the line through parallel to and the line through parallel to . Suppose that the tangents to at and meet at a point . Prove that the three lines and are either parallel or concurrent.
Proposed by Irena Majcen and Kris Stopar, Slovenia
Proposed by Irena Majcen and Kris Stopar, Slovenia
Izvor: Međunarodna matematička olimpijada, shortlist 2011