MathDB
1 of distances AM, BM, CM is equal to sum of 2 other distances.

Source: TOT 356 1992 Autumn O S5 - Tournament of Towns

June 10, 2024
geometry

Problem Statement

The bisector of the angle AA of triangle ABCABC intersects its circumscribed circle at the point DD. Suppose PP is the point symmetric to the incentre of the triangle with respect to the midpoint of the side BCBC, and MM is the second intersection point of the line PDPD with the circumscribed circle. Prove that one of the distances AMAM, BMBM, CMCM is equal to the sum of two other distances.
(VO Gordon)