olymmath

IGO 2019 A4

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Given an acute non-isosceles triangle ABCABC with circumcircle Γ\Gamma . MM is the midpoint of segment BCBC and NN is the midpoint of arc BCBC of Γ\Gamma (the one that doesn't contain AA ). XX and YY are points on Γ\Gamma such that BX∥CY∥AMBX\parallel CY\parallel AM . Assume there exists point ZZ on segment BCBC such that circumcircle of triangle XYZXYZ is tangent to BCBC . Let ω\omega be the circumcircle of triangle ZMNZMN . Line AMAM meets ω\omega for the second time at PP . Let KK be a point on ω\omega such that KN∥AMKN\parallel AM , ωb\omega_b be a circle that passes through BB , XX and tangents to BCBC and ωc\omega_c be a circle that passes through CC , YY and tangents to BCBC . Prove that circle with center KK and radius KPKP is tangent to 3 circles ωb\omega_b , ωc\omega_c and Γ\Gamma .

Proposed by Tran Quan - Vietnam

Dataset text AI-MO AoPS. Quoted with source.

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