 # Lesson 2 5 Proving Lines Parallel Lesson 2

• Slides: 7 Lesson 2 - 5 Proving Lines Parallel Lesson 2 -5: Proving Lines Parallel 1 Proving Lines Parallel - Postulates & Theorems l If two lines are cut by a transversal and corresponding angles are congruent, then the lines are parallel. Lesson 2 -5: Proving Lines Parallel 2 Proving Lines Parallel - Postulates &Theorems l If two lines are cut by a transversal and alternate interior angles are congruent, then the lines are parallel. Lesson 2 -5: Proving Lines Parallel 3 Proving Lines Parallel - Postulates &Theorems l If two lines are cut by a transversal and consecutive interior angles are supplementary, then the lines are parallel. Lesson 2 -5: Proving Lines Parallel 4 Proving Lines Parallel - Postulates &Theorems l If two lines are cut by a transversal and consecutive exterior angles are supplementary, then the lines are parallel. Lesson 2 -5: Proving Lines Parallel 5 Examples: Proving Lines Parallel Find the value of x which will make lines a and lines b parallel. 2. 1. l 3. 4. Answers: 1. 20° 2. 50° 3. 90° 4. 20° Lesson 2 -5: Proving Lines Parallel 6 Ways to Prove Two Lines Parallel l l Show that corresponding angles are equal. Show that alternative interior angles are equal. Show that consecutive interior angles are supplementary. Show that consecutive exterior angles are supplementary. In a plane, show that the lines are perpendicular to the same line. Lesson 2 -5: Proving Lines Parallel 7