Ways of proving a quadrilaterals are parallelograms Section 5-2

Using the definition If both sets of opposite sides are parallel, then the quadrilateral is a parallelogram.

Using both sets of opposite sides If both pairs of opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram

Using one set of opposite sides If one pair of opposite sides of a quadrilateral is both congruent, and parallel, then the quadrilateral is a parallelogram

Using opposite angles If both pairs of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram

Using Diagonals If the diagonals of a quadrilateral bisect each other, then the quadrilateral is a parallelogram.