1. Proving a quadrilateral is a parallelogram
Using coordinate geometry…

2. To prove a quad. is a parallelogram
1) Use the slope formula 4 times to show BOTH pairs of opposite sides are parallel (have the same slope)
and write the concluding statement:
Quad. is a parallelogram bc both pairs of opposite sides are parallel

3. OR
Use the distance formula 4 times to show BOTH pairs of opposite sides are congruent(have the same length)
and write the concluding statement:
Quad is a parallelogram bc both pairs of opp. sides congruent

4. OR
Use the midpoint formula 2 times to show both diagonals bisect each other
(we don’t use this one often!)