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ISL 2020 G6

    Let II and IAI_{A} be the incenter and the AA-excenter of an acute-angled triangle ABCA B C with AB<ACA B<A C. Let the incircle meet BCB C at DD. The line ADA D meets BIAB I_{A} and CIAC I_{A} at EE and FF, respectively. Prove that the circumcircles of triangles AIDA I D and IAEFI_{A} E F are tangent to each other. (Slovakia)

    Dataset text NuminaMath olympiads-ref. Quoted with source.

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