1. Entry Task
Pick one of the theorems or the postulate from the last lesson and write the converse of that statement.
Same Side Interior Angles Postulate
Corresponding Angles Theorem
Alternate Interior Angles Theorem
Alternate Exterior Angles Theorem
Do you think the converse is true? Explain.

2. Proving Lines Parallel
Lesson 3-3

3. Learning Targets I will be able to:
Use angle relationships to determine if lines are parallel;
Prove theorems about lines and angles.

4. Original Theorems and Postulate
If parallel lines are intersected by a transversal, then
each pair of same side interior angles are supplementary;
each pair of corresponding angles are congruent;
each pair of alternate interior angles are congruent;
each pair of alternate exterior angles are congruent.

5. Converse of Corresponding Angles Theorem
If two lines and a transversal form corresponding angles that are congruent, then the two lines are parallel.

6. Converse of Alternate Interior Angles Theorem
If two lines and a transversal form alternate interior angles that are congruent, then the two lines are parallel.

7. Converse of Alternate Exterior Angles Theorem
If two lines and a transversal form alternate exterior angles that are congruent, then the two lines are parallel.

8. Converse of Same-Side Interior Angles Postulate
If two lines and a transversal form same-side interior angles that are supplementary, then the two lines are parallel.

9. Example of a Flow Proof
This is a proof of the Converse of the Alternate Interior Angles Theorem

10. Use the information and diagram below to write a flow proof.

11. Examples
1. 2.

12. Lesson Check – page 160

13. Assignment
Page 160 (7-32 all)