olymmath

ISL 2019 G1

    Let ABCA B C be a triangle. Circle Γ\Gamma passes through AA, meets segments ABA B and ACA C again at points DD and EE respectively, and intersects segment BCB C at FF and GG such that FF lies between BB and GG. The tangent to circle BDFB D F at FF and the tangent to circle CEGC E G at GG meet at point TT. Suppose that points AA and TT are distinct. Prove that line ATA T is parallel to BCB C. (Nigeria)

    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.

    Solutions

    Official solution Solution 1 by the IMO Problem Selection Committee

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