MathDB
perpendicular wanted, right isosceles, square (2014 Romanian NMO grade VII P4)

Source:

May 28, 2020
geometrysquareperpendicularisoscelesright triangle

Problem Statement

Outside the square ABCDABCD is constructed the right isosceles triangle ABDABD with hypotenuse [AB][AB]. Let NN be the midpoint of the side [AD][AD] and M=CEAB{M} = CE \cap AB, P=CNAB{P} = CN \cap AB , F=PEMN{F} = PE \cap MN. On the line FPFP the point QQ is considered such that the [CE[CE is the bisector of the angle QCBQCB. Prove that MQCFMQ \perp CF.