Given a triangle ABC, a line δ and a constant k, distinct from 0 and 1,M a variable point on the line δ. Points E,F are on MB,MC respectively such that MBME=MCMF=k. Points P,Q are on AB,AC such that PE,QF are perpendicular to δ. Prove that the line through M perpendicular to PQ has a fixed point.Nguyễn Minh Hà
fixedFixed pointequal ratiogeometry