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RMO 2025 K5

  • KV and JNV

Let ABCABC be an acute-angled triangle with ∠BAC=60∘\angle BAC = 60^\circ and AB<BC<ACAB < BC < AC . Let M,NM, N be the midpoints of AB,ACAB, AC respectively. Suppose BE,CFBE, CF are altitudes, with EE on CACA and FF on ABAB . Let XX be the image of MM under reflection in the midpoint of BFBF , and YY be the image of NN under reflection in the midpoint of CECE . Prove that XYXY bisects BCBC .

Proposed by - Rijul Saini

Dataset text AI-MO AoPS. Quoted with source.

Official text: Indian Regional Mathematical Olympiad 2025 official paper, page 1.

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