ISL 2018 G7
Let be the circumcentre, and be the circumcircle of an acute-angled triangle . Let be an arbitrary point on , distinct from , and their antipodes in . Denote the circumcentres of the triangles , and by , and , respectively. The lines , and perpendicular to , and pass through , and , respectively. Prove that the circumcircle of the triangle formed by , and is tangent to the line . (Russia)
Dataset text NuminaMath olympiads. Quoted with source.
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