# Angles Formed by Parallel Lines Angles Formed by

Angles Formed by Parallel Lines Angles Formed by Parallel 3 -2 and Transversals Warm Up Lesson Presentation Lesson Quiz Holt Geometry Holt Mc. Dougal Geometry Lines

3 -2 Angles Formed by Parallel Lines and Transversals Warm Up Identify each angle pair. 1. 1 and 3 corr. s 2. 3 and 6 alt. int. s 3. 4 and 5 alt. ext. s 4. 6 and 7 same-side int s Holt Mc. Dougal Geometry

3 -2 Angles Formed by Parallel Lines and Transversals Objective Prove and use theorems about the angles formed by parallel lines and a transversal. Holt Mc. Dougal Geometry

3 -2 Angles Formed by Parallel Lines and Transversals Corresponding Angles are Congruent Holt Mc. Dougal Geometry

3 -2 Angles Formed by Parallel Lines and Transversals Alt. Int. s are ≅ Alt. Ext. s are ≅ SSI s are supplementary Holt Mc. Dougal Geometry

3 -2 Angles Formed by Parallel Lines and Transversals Example 1: Using the Corresponding Angles Postulate Find each angle measure. A. m ECF x = 70 Corr. s Post. m ECF = 70° B. m DCE 5 x = 4 x + 22 x = 22 m DCE = 5 x = 5(22) = 110° Holt Mc. Dougal Geometry Corr. s Post. Subtract 4 x from both sides. Substitute 22 for x.

3 -2 Angles Formed by Parallel Lines and Transversals Example 2: Finding Angle Measures Find each angle measure. A. m EDG = 75° Alt. Ext. s Thm. B. m BDG x – 30° = 75° Alt. Ext. s Thm. x = 105 Add 30 to both sides. m BDG = 105° Holt Mc. Dougal Geometry

3 -2 Angles Formed by Parallel Lines and Transversals Check It Out! Example 1 Find m QRS. x = 118 Corr. s Post. m QRS + x = 180° m QRS = 180° – x Def. of Linear Pair Subtract x from both sides. = 180° – 118° Substitute 118° for x. = 62° Holt Mc. Dougal Geometry

3 -2 Angles Formed by Parallel Lines and Transversals Check It Out! Example 2 Find m ABD. 2 x + 10° = 3 x – 15° Alt. Int. s Thm. x = 25 Subtract 2 x and add 15 to both sides. m ABD = 2(25) + 10 = 60° Substitute 25 for x. Holt Mc. Dougal Geometry

3 -2 Angles Formed by Parallel Lines and Transversals Classwork/Homework • Chapter 3 Section 2 #’s: 1 -4 all, 6 -11 all, 20 -23 all Holt Mc. Dougal Geometry

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