olymmath

ISL 2020 G3

    Let ABCDA B C D be a convex quadrilateral with ∠ABC>90∘,∠CDA>90∘\angle A B C>90^{\circ}, \angle C D A>90^{\circ}, and ∠DAB=∠BCD\angle D A B=\angle B C D. Denote by EE and FF the reflections of AA in lines BCB C and CDC D, respectively. Suppose that the segments AEA E and AFA F meet the line BDB D at KK and LL, respectively. Prove that the circumcircles of triangles BEKB E K and DFLD F L are tangent to each other. (Slovakia)

    Dataset text NuminaMath olympiads. Quoted with source.

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