olymmath

ISL 2019 G4

    Let PP be a point inside triangle ABCA B C. Let APA P meet BCB C at A1A_{1}, let BPB P meet CAC A at B1B_{1}, and let CPC P meet ABA B at C1C_{1}. Let A2A_{2} be the point such that A1A_{1} is the midpoint of PA2P A_{2}, let B2B_{2} be the point such that B1B_{1} is the midpoint of PB2P B_{2}, and let C2C_{2} be the point such that C1C_{1} is the midpoint of PC2P C_{2}. Prove that points A2,B2A_{2}, B_{2}, and C2C_{2} cannot all lie strictly inside the circumcircle of triangle ABCA B C. (Australia)

    Official text Transcription from NuminaMath olympiads, checked word for word against the official paper. Quoted with source.

    Official text: IMO 2019 Shortlist booklet, page 10.

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