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Lesson 3.2 Proof and Perpendicular Lines. D. A. B. C. Theorem 3.1. If two lines intersect to form a linear pair of congruent angles, then the lines are Ex 1. m<ABD = m<DBC and a linear pair, DB AC. F. J. G. H. Theorem 3.2.
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D A B C Theorem 3.1 • If two lines intersect to form a linear pair of congruent angles, then the lines are • Ex 1 m<ABD = m<DBC and a linear pair, DB AC
F J G H Theorem 3.2 • If two sides of two adjacent acute angles are perpendicular, then the angles are complementary. • Ex. 2 <FGJ is complementary to <JGH
Examples: Solve for x 1. x 60° ANSWER: 60 + x = 90 -60 -60 x = 30
x 55° Example 2 ANSWER: x + 55 = 90 -55 -55 x = 35
27° (2x-9)° Example 3 ANSWER: 2x – 9 + 27 = 90 2x +18 = 90 2x = 72 x = 36
l m Theorem 3.3 • If 2 lines are perpendicular, then they intersect to form four right angles.