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SHARYGIN 2022 Problem 24

    Let OABCDEFOABCDEF be a hexagonal pyramid with base ABCDEFABCDEF circumscribed around a sphere ω\omega . The plane passing through the touching points of ω\omega with faces OFAOFA , OABOAB and ABCDEFABCDEF meets OAOA at point A1A_1 , points B1B_1 , C1C_1 , D1D_1 , E1E_1 and F1F_1 are defined similarly. Let ℓ\ell , mm and nn be the lines A1D1A_1D_1 , B1E1B_1E_1 and C1F1C_1F_1 respectively. It is known that ℓ\ell and mm are coplanar, also mm and nn are coplanar. Prove that ℓ\ell and nn are coplanar.

    Dataset text AI-MO AoPS. Quoted with source.

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