MathDB
Geometry problem

Source: EGMO 2018 Moldova TST

February 11, 2018
geometry

Problem Statement

Let ABC\triangle ABC be an acute triangle.OO denote its circumcenter.Points DD,EE,FF are the midpoints of the sides BCBC,CACA,and ABAB.Let MM be a point on the side BCBC . AMEF={N} AM \cap EF = \big\{ N \big\} . ON(ODM)={P}ON \cap \big( ODM \big) = \big\{ P \big\} Prove that MM' lie on (DEF)\big(DEF\big) where MM' is the symmetrical point of MM thought the midpoint of DPDP.