olymmath

ISL 2012 G8

    Let ABCA B C be a triangle with circumcircle ω\omega and ℓ\ell a line without common points with ω\omega. Denote by PP the foot of the perpendicular from the center of ω\omega to ℓ\ell. The side-lines BC,CA,ABB C, C A, A B intersect ℓ\ell at the points X,Y,ZX, Y, Z different from PP. Prove that the circumcircles of the triangles AXP,BYPA X P, B Y P and CZPC Z P have a common point different from PP or are mutually tangent at PP.

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

    Official text: IMO 2012 Shortlist booklet, page 6.

    Solutions

    Official solution Solution 1 by the IMO Problem Selection Committee

    The terms of the source let olymmath link to this solution but not copy it. Read the solution (IMO official site).

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