1. 3-1 Properties of Parallel Lines
GEOMETRY

2. Vocabulary
A transversal is a line that intersects two coplanar lines at two distinct points. (8 angles are formed)

3. 4 Types of Angles Alternate Interior Angles Same-side Interior Angles
Corresponding Angles
Alternate Exterior Angles

4. Example 1: Identifying Angles
Same side Interior Angles
Corresponding Angles

5. Postulate 3-1: Corresponding Angles
If a transversal intersects two parallel lines, then corresponding angles are congruent.
Example:

6. Alternate Interior/Exterior Angles
If a transversal intersects two parallel lines, then alternate interior angles and the alternate exterior angles are congruent.
Example:

7. Same Side Interior Angles
If a transversal intersects two parallel lines, then same-side interior angles are supplementary.
Example:

8. EXAMPLE 2: Finding Measures of Angles.

9. Example 3: Using algebra to find Angle Measures