olymmath

ISL 2016 G2

    Let ABCA B C be a triangle with circumcircle Γ\Gamma and incentre II. Let MM be the midpoint of side BCB C. Denote by DD the foot of perpendicular from II to side BCB C. The line through II perpendicular to AIA I meets sides ABA B and ACA C at FF and EE respectively. Suppose the circumcircle of triangle AEFA E F intersects Γ\Gamma at a point XX other than AA. Prove that lines XDX D and AMA M meet on Γ\Gamma.

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

    Official text: IMO 2016 Shortlist booklet, page 10.

    Solutions

    Official solution Solution 1 by the IMO Problem Selection Committee

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