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prove that L_1 and L_2 are equidistant from line AB

Source: Sharygin Geometry Olympiad 2014 Correspondence Round P12

August 1, 2018
geometrycircumcirclecircles

Problem Statement

Circles ω1\omega_1 and ω2\omega_2 meet at points AA and BB. Let points K1K_1 and K2K_2 of ω1\omega_1 and ω2\omega_2 respectively be such that K1AK_1A touches ω2\omega_2, and K2AK_2A touches ω1\omega_1. The circumcircle of triangle K1BK2K_1BK_2 meets lines AK1AK_1 and AK2AK_2 for the second time at points L1L_1 and L2L_2 respectively. Prove that L1L_1 and L2L_2 are equidistant from line ABAB.