ABC is an acute triangle(all the three angles are acute).

D,E,F are points on BC,CA,AB respectively such that AD,BE,CF are the altitudes of the triangle.

FP is perpendicular to BC, P lying on BC

FQ is perpendicualr to AC, Q lying on AC

FM is perpendicular to AD, M lying on AD

FN is perpendicualr to BE, N lying on BE

Prove that P,Q,M,N are collinear points.

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Malay