# Lesson 14 2 Parallel Lines and Transversals Parallel

• Slides: 10

Lesson 14. 2: Parallel Lines and Transversals Parallel lines are lines in the same plane that do not intersect.

Angles formed by Transversals A transversal is a line that intersects two or more coplanar lines at different points. • Angles that are between the two lines that are cut by the transversal are called interior angles. Angles 2, 4, 5 and 7 are interior angles. • Angles that are not interior angles are called exterior angles. Angles 1, 3, 6 and 8 are exterior angles.

Special Angle Pairs formed by Transversals form special pairs of angles: • Corresponding Angles • Alternate Interior Angles • Alternate Exterior Angles • Same side Interior Angles

Examples 3. Corresponding angles 4. Alternate Exterior angles 5. Alternate Interior angles

Postulate Same-Side Interior Angles Postulate If two parallel lines are cut by a transversal, then the pairs of same-side interior angles are supplementary.

Theorems Alternate Interior Angles Theorem If two parallel lines are cut by a transversal, then the pairs of alternate interior angles are congruent. Alternate Exterior Angles Theorem If two parallel lines are cut by a transversal, then the pairs of alternate exterior angles are congruent.

Your Turn Complete the proof of the on pg. 691 in your textbook. Change the prove.

One More Theorem Corresponding Angles Theorem If two parallel lines are cut by a transversal, then the pairs of corresponding angles are congruent.

Prove the Corresponding Angles Theorem