1. 3-1 Properties of Parallel Lines M11.B 2.3.11.A
Objectives:
To identify angles formed by two lines and a transversal
To prove and use properties of parallel lines

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

3. 4 Types of Angles Alternate interior angles Same-side interior angles
Corresponding angles
Alternate exterior angles 6 5 3 1 2 4 8 7

4. Example: Identifying Angles
Same side Interior Angles
Corresponding Angles 1 4 8 5 3 2 6 7

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

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

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

8. Find the measure of each missing angle…Justify your answer

9. Vocabulary - Review
Straight Angle – Angle(s) measure 180° to form a straight angle.

10. Example: Using algebra to find Angle Measures
2x y (y - 50)