olymmath

ISL 2015 G2

    Let ABCA B C be a triangle inscribed into a circle Ω\Omega with center OO. A circle Γ\Gamma with center AA meets the side BCB C at points DD and EE such that DD lies between BB and EE. Moreover, let FF and GG be the common points of Γ\Gamma and Ω\Omega. We assume that FF lies on the arc ABA B of Ω\Omega not containing CC, and GG lies on the arc ACA C of Ω\Omega not containing BB. The circumcircles of the triangles BDFB D F and CEGC E G meet the sides ABA B and ACA C again at KK and LL, respectively. Suppose that the lines FKF K and GLG L are distinct and intersect at XX. Prove that the points A,XA, X, and OO are collinear. (Greece)

    Dataset text NuminaMath olympiads. Quoted with source.

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