1. 6-2 Properties of Parallelograms

2. Parallelogram: a quadrilateral with both pairs of opposite sides parallel. In a quadrilateral, opposite sides do not share a vertex and opposite angles do not share a side.

3. Theorem 6-3
If a quadrilateral is a parallelogram, then its opposite sides are congruent

4. Angles of a polygon that share a side are consecutive angles

5. Theorem 6-4
If a quadrilateral is a parallelogram, then its consecutive angles are supplementary (b/c they are same-side interior angles)

6. Problem 1: Using Consecutive Angles

7. 86°

8. Theorem 6-5
If a quadrilateral is a parallelogram, then its opposite angles are congruent

9. Problem 2: Using Properties of Parallelograms in a Proof

10. Theorem 6-6
If a quadrilateral is a parallelogram, then its diagonals bisect each other

11. Problem 3: Using Algebra to Find Lengths

13. Theorem 6-7
If three (or more) parallel lines cut off congruent segments on one transversal, then they cut off congruent segment on every transversal.

14. Problem 4: Using Parallel Lines and Transversals