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15th Junior Turkish Mathematical Olympiad

Turkey geometry

Problem

A circle that passes through the vertex of a rectangle intersects the side at a second point different from . A line passing through is tangent to this circle at a point , and the circle with center and passing through intersects the side at the point . Show that if , then .

problem
Solution
Let be the point of intersection of the lines and . Since , the lines and are perpendicular.



On the other hand, implies that the triangles and are similar and . Therefore , and .

Techniques

TangentsAngle chasingDistance chasing