IMO Shortlist 2004 problem G2
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Avg: 6,0 Let be a circle and let be a line such that and have no common points. Further, let be a diameter of the circle ; assume that this diameter is perpendicular to the line , and the point is nearer to the line than the point . Let be an arbitrary point on the circle , different from the points and . Let be the point of intersection of the lines and . One of the two tangents from the point to the circle touches this circle at a point ; hereby, we assume that the points and lie in the same halfplane with respect to the line . Denote by the point of intersection of the lines and . Let the line intersect the circle at a point , different from .
Prove that the reflection of the point in the line lies on the line .
Prove that the reflection of the point in the line lies on the line .
Izvor: Međunarodna matematička olimpijada, shortlist 2004