ISL 2021 G2
Let be a convex quadrilateral circumscribed around a circle with centre . Let be the circumcircle of the triangle . The extensions of and beyond and meet at and , respectively. The extensions of and beyond meet at and , respectively. Prove that the perimeters of the (possibly self-intersecting) quadrilaterals and are equal.
Official text Transcription from NuminaMath olympiads, checked word for word against the official paper. Quoted with source.
Official text: IMO 2021 Shortlist booklet, page 8.
Solutions
Official solution Solution 1 by the IMO Problem Selection Committee
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