JBMO-SL 2019 G2
Let be a triangle and let be its circumcircle. Let and be two parallel lines passing through and respectively. The lines and intersect with for the second time at the points and respectively, with belonging on the arc , and on the arc . Suppose that intersects at , and intersects at . If and are the circumcenters of the triangles and respectively, and is the center of the circumcircle of the triangle , prove that is parallel to and .
Dataset text NuminaMath olympiads. Quoted with source.
Solutions
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