MathDB
concyclic wanted with center on the line connecting excenters

Source: 2020 XXIII All-Ukrainian Tournament of Young Mathematicians named after M. Y. Yadrenko, Qualifying p13

May 4, 2021
geometryConcyclicexcenterUkrainian TYM

Problem Statement

In the triangle ABCABC on the side BCBC, the pointsD D and EE are chosen so that the angle BADBAD is equal to the angle EACEAC. Let II and JJ be the centers of the inscribed circles of triangles ABDABD and AECAEC respectively, FF be the point of intersection of BIBI and EJEJ, GG be the point of intersection of DIDI and CJCJ. Prove that the points I,J,F,GI, J, F, G lie on one circle, the center of which belongs to the line IbIcI_bI_c, where IbI_b and IcI_c are the centers of the exscribed circles of the triangle ABCABC, which touch respectively sides ACAC and ABAB.