IMO Shortlist 2012 problem G8
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Avg: 9,0 Let be a triangle with circumcircle and a line without common points with . Denote by the foot of the perpendicular from the center of to . The side-lines intersect at the points different from . Prove that the circumcircles of the triangles , and have a common point different from or are mutually tangent at .
Izvor: Međunarodna matematička olimpijada, shortlist 2012