100 likes | 596 Views
Proving Lines Parallel. Postulate 3-2: Converse of the Corresponding Angles Postulate. If two lines are cut by a transversal and corresponding angles are congruent , then the lines are parallel. Theorem 3-4: Converse of the Alternate Interior Angles Theorem.
E N D
Postulate 3-2: Converse of the Corresponding Angles Postulate • If two lines are cut by a transversal and corresponding angles are congruent, then the lines are parallel.
Theorem 3-4: Converse of the Alternate Interior Angles Theorem • If two lines are cut by a transversal and alternate interior angles are congruent, then the lines are parallel.
Postulate 3-6: Converse of the Alternate Exterior Angles Postulate • If two lines are cut by a transversal and alternate exterior angles are congruent, then the lines are parallel.
Theorem 3-3: Converse of the Consecutive (Same-Side) Interior Angles Theorem • If two lines are cut by a transversal and consecutive interior angles are supplementary, then the lines are parallel.
Consecutive Exterior Angles • If two lines are cut by a transversal and consecutive exterior angles are supplementary, then the lines are parallel.
2. 1. 3. 4. Examples: Proving Lines Parallel • Find the value of x which will make lines a and lines b parallel. Answers: 1. 20° 2. 50° 3. 90° 4. 20°
Ways to Prove Two Lines Parallel • 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.