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KöMaL 2025 A920

    Given a non-isosceles triangle ABCABC, let its circumcircle be denoted by Ω\Omega. Let ωA\omega_A be the mixtilinear incircle corresponding to vertex AA (that is, the circle tangent to sides ABAB, ACAC, and internally tangent to Ω\Omega). Define ωB\omega_B and ωC\omega_C analogously. Let the points where ωA,ωB,ωC\omega_A,\omega_B,\omega_C touch Ω\Omega be denoted by TA,TB,TCT_A, T_B, T_C, respectively. Show that the Monge line of the circles ωA,ωB,ωC\omega_A,\omega_B,\omega_C (that is, the line passing through the pairwise external homothety centers of the three circles) coincides with the Pascal line of the hexagon ATCBTACTBAT_CBT_ACT_B (that is, the line passing through the points ATC∩TACAT_C \cap T_AC, TCB∩CTBT_CB \cap CT_B, BTA∩TBABT_A \cap T_BA).

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