In marketing transactions, the fact that customers who buy product x also buy product y creates a opportunity. that is, "if they're buying x, sell them y" or "if they're buying y, sell them x."

If the angle bisectors of a pair of opposite angles of a quadrilateral are the opposite sides of a parallelogram formed by the two angle bisectors and two sides of the quadrilateral, is the quadrilateral always a parallelogram? explain your answer.