1. A quadrilateral nABCD is called a trapezoid if either (‘AB (‘CD or (‘BC (‘AD . Prove that every..

1. A quadrilateral nABCD is called a trapezoid if either ('AB  ('CD or ('BC  ('AD . Prove that every trapezoid is convex. 2. Prove that a quadrilateral is convex if the diagonals have a point in common (the remaining part of Theorem 4.6.8