Given is the non-right triangle ABC. D,E and F are the feet of the respective altitudes from A,B and C. P,Q and R are the respective midpoints of the line segments EF, FD and DE. p⊥BC passes through P, q⊥CA passes through Q and r⊥AB passes through R. Prove that the lines p,q and r pass through one point. concurrencyconcurrentgeometry