Let ABCD be a trapezium with bases AB and CD such that AB=2CD. From A the line r is drawn perpendicular to BC and from B the line t is drawn perpendicular to AD. Let P be the intersection point of r and t. From C the line s is drawn perpendicular to BC and from D the line u perpendicular to AD. Let Q be the intersection point of s and u. If R is the intersection point of the diagonals of the trapezium, prove that points P,Q and R are collinear. geometrytrapezoidcollinearperpendicular