ISL 2021 G7
A point is chosen inside an acute-angled triangle with so that . A point is constructed on the segment so that . Similarly, a point is constructed on the segment so that . A point is chosen on the line so that . Let and be the circumcentres of the triangles and . Prove that the lines , and are concurrent.
Dataset text NuminaMath olympiads. Quoted with source.
Official text: IMO 2021 Shortlist booklet, page 9.
Solutions
Official solution Solution 1 by the IMO Problem Selection Committee
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