JBMO-SL 2016 G7
Let be a chord of a circle centered at , and let be a point on the segment such that . Two circles through , internally tangent to (c) at and , respectively, meet again at . Let be one of the points of intersection of the line and the circle (c), and let the lines and meet at . Prove that the line is tangent to the circle .

Dataset text NuminaMath olympiads. Quoted with source.
Solutions
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