olymmath

JBMO-SL 2020 G1

  • Answer

Let △ABC\triangle A B C be an acute triangle. The line through AA perpendicular to BCB C intersects BCB C at DD. Let EE be the midpoint of ADA D and ω\omega the the circle with center EE and radius equal to AEA E. The line BEB E intersects ω\omega at a point XX such that XX and BB are not on the same side of ADA D and the line CEC E intersects ω\omega at a point YY such that CC and YY are not on the same side of ADA D. If both of the intersection points of the circumcircles of △BDX\triangle B D X and △CDY\triangle C D Y lie on the line ADA D, prove that AB=ACA B=A C.

Dataset text NuminaMath olympiads. Quoted with source.

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A B=A C

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