### Proving a Quadrilateral a Parallelogram | Geometry Proof How To Help

In this video geometry lesson, I prove two parallelogram theorems. The first is: If the diagonals of a quadrilateral bisect each other, then the quadrilateral is a parallelogram. The other theorem I prove is: If both pairs of opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram. I use the theorems: If both pairs of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram and If one pair of opposite sides of a quadrilateral is both congruent and parallel, then the quadrilateral is a parallelogram to solve problems.

Length:
21:31