Table of Contents page 7: 3-5 Proving Lines Parallel page 8: 3-5 Practice

Lesson 3-5 Proving Lines Parallel Objectives: Recognize angle conditions that occur with parallel lines and prove that two lines are parallel based on the angle relationships. Monday, October 26, 2009

Postulates and Theorems Postulate 3.4 – If two lines in a plane are cut by a transversal so that corresponding angles are congruent, then the lines are parallel. Parallel Postulate – If there is a line and a point not on the line, then there exists exactly one line through the point that is parallel to the given line Theorem If two lines in a plane are cut by a transversal so that a pair of alternate exterior angles are congruent, then the lines are parallel.

Theorem If two lines in a plane are cut by a transversal so that a pair of consecutive interior angles are supplementary, then the lines are parallel Theorem If two lines in a plane are cut by a transversal so that a pair of alternate interior angles are congruent, then the lines are parallel Theorem 3.8 – In a plane, if two lines are perpendicular to the same line, then they are parallel.

Example 1 Find the value of x so that l || p V S B T U l p (3x – 4)° (12x – 11)°

Example 2 Find the value of x so l || p V S B T U l p (9x – 11)° (8x +4)°

Assignment Tear out page 37 in your workbook. Staple it to page 8 in your interactive notebook. Complete the problems on that page.