1. Six Properties of Parallelograms
5-2 Proving Quadrilaterals are Parallelograms
Six Properties of Parallelograms
Opposite sides are parallel. (definition)
Opposite sides of a parallelogram are congruent.
Opposite angles of a parallelogram are congruent.
Diagonals of a parallelogram bisect each other.
Consecutive (same-side interior) angles are supplementary.
Either diagonal separates the parallelogram into two congruent triangles.

2. Definition used to prove that Quadrilaterals are Parallelograms
If both pairs of opposite sides of a quadrilateral are parallel, then the quadrilateral is a parallelogram.

3. Theorems used to prove that Quadrilaterals are Parallelograms
If both pairs of opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram.
If one pair of opposite sides of a quadrilateral are both congruent and parallel, then the quadrilateral is a parallelogram.

4. (More) Theorems used to prove that Quadrilaterals are Parallelograms
If both pairs of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram.
If the diagonals of a quadrilateral bisect each other, then the quadrilateral is a parallelogram.

5. Homework Section 5.2 Classroom Exercises (p. 173) #1-9
Section 5.2 Written Exercises (p )
#1-7, 10, & 19-22