MathDB
Cyclic Quad

Source: USAMO 2008 Problem 2

May 1, 2008
geometrycircumcirclegeometric transformationhomothetygeometry solvedsymmedianAngle Chasing

Problem Statement

Let ABC ABC be an acute, scalene triangle, and let M M, N N, and P P be the midpoints of BC \overline{BC}, CA \overline{CA}, and AB \overline{AB}, respectively. Let the perpendicular bisectors of AB \overline{AB} and AC \overline{AC} intersect ray AM AM in points D D and E E respectively, and let lines BD BD and CE CE intersect in point F F, inside of triangle ABC ABC. Prove that points A A, N N, F F, and P P all lie on one circle.