olymmath

ISL 2020 G8

    Let Γ\Gamma and II be the circumcircle and the incenter of an acute-angled triangle ABCA B C. Two circles ωB\omega_{B} and ωC\omega_{C} passing through BB and CC, respectively, are tangent at II. Let ωB\omega_{B} meet the shorter arc ABA B of Γ\Gamma and segment ABA B again at PP and MM, respectively. Similarly, let ωC\omega_{C} meet the shorter arc ACA C of Γ\Gamma and segment ACA C again at QQ and NN, respectively. The rays PMP M and QNQ N meet at XX, and the tangents to ωB\omega_{B} and ωC\omega_{C} at BB and CC, respectively, meet at YY. Prove that the points A,XA, X, and YY are collinear. (Netherlands)

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

    Official text: IMO 2020 Shortlist booklet, page 11.

    Solutions

    Official solution Solution 1 by the IMO Problem Selection Committee

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