olymmath

ISL 2014 G7

    Let ABCA B C be a triangle with circumcircle Ω\Omega and incentre II. Let the line passing through II and perpendicular to CIC I intersect the segment BCB C and the arc⁡BC(\operatorname{arc} B C( not containing A)A) of Ω\Omega at points UU and VV, respectively. Let the line passing through UU and parallel to AIA I intersect AVA V at XX, and let the line passing through VV and parallel to AIA I intersect ABA B at YY. Let WW and ZZ be the midpoints of AXA X and BCB C, respectively. Prove that if the points I,XI, X, and YY are collinear, then the points I,WI, W, and ZZ are also collinear.

    Dataset text NuminaMath olympiads. Quoted with source.

    Official text: IMO 2014 Shortlist booklet, page 9.

    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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