There are 5 distinct ways to know that a quadrilateral is a paralleogram. If a quadrilateral meets any of the 5 criteria below, then it must be a parallelogram.
Criteria proving a quadrilateral is parallelogram
- 1) If a quadrilateral has one pair of sides that are both parallel and congruent.
- 2) If all opposite sides of the quadrilateral are congruent.
- 3) Both pairs of opposite sides are parallel.
- 4) Opposite angles are congruent.
- 5) Diagonals bisect.