MathDB
intersection of circles (M,ME) and (N,NF) lies on AB

Source: (2021 -) 2022 Dürer Math Competition Regional E+4 https://artofproblemsolving.com/community/c1621671_

November 30, 2022
geometrycollinear

Problem Statement

Let ABCABC be an acute triangle, and let FAF_A and FBF_B be the midpoints of sides BCBC and CACA, respectively. Let EE and FF be the intersection points of the circle centered at FAF_A and passing through AA and the circle centered at FBF_B and passing through BB. Prove that if segments CECE and CFCF have midpoints NN and MM, respectively, then the intersection points of the circle centered at MM and passing through EE and the circle centered at NN and passing through FF lie on the line ABAB.