1. Proving Lines Parallel
Lesson 3-5
Proving Lines Parallel

2. Proving Lines Parallel - Postulates & Theorems
If two lines are cut by a transversal and corresponding angles are congruent, then the lines are parallel.

3. Proving Lines Parallel - Postulates & Theorems
If two lines are cut by a transversal and alternate interior angles are congruent, then the lines are parallel.

4. Proving Lines Parallel - Postulates & Theorems
If two lines are cut by a transversal and consecutive interior angles are supplementary, then the lines are parallel.

5. Proving Lines Parallel - Postulates & Theorems1 b 2
Converse of Alternate Exterior Angles Theorem
If two lines and a transversal intersects form alternate exterior angles that are congruent, then the two lines are parallel.

6. Proving Lines Parallel - Postulates & Theorems
If two lines are perpendicular to the same transversal then they are parallel.

7. Examples: Proving Lines Parallel
Find the value of x which will make lines a and lines b parallel. 2. 1. 3. 4.
1. 20°
2. 50°
3. 90°
4. 20°
Answers:

8. Proving Lines Parallel - Postulates & Theorems
Show that corresponding angles are congruent.
Show that alternative interior angles are congruent.
Show that consecutive interior angles are supplementary.
In a plane, show that the lines are perpendicular to the same line.
Lesson 2-5: Proving Lines Parallel

9. HOMEWORK
Pg #1-23 all 25-28