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TSTST 2025 Problem 9

    Let acute triangle ABCABC have orthocenter HH. Let B1B_1, C1C_1, B2B_2, and C2C_2 be collinear points which lie on lines ABAB, ACAC, BHBH, and CHCH, respectively. Let ωB\omega_B and ωC\omega_C be the circumcircles of triangles BB1B2BB_1B_2 and CC1C2CC_1C_2, respectively. Prove that the radical axis of ωB\omega_B and ωC\omega_C intersects the line through their centers on the nine-point circle of triangle ABCABC.

    Official text USA TST for the TST 2025 official paper, page 3. Quoted with source.

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