3-5 Proving Lines Parallel

# 3-5 Proving Lines Parallel - given line. • Through a...

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Proving Lines Parallel Section 3-5

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Postulate 3.4 If 2 lines are cut by a transversal so that corresponding angles are congruent, then the lines are parallel. 60 60
Parallel Line Theorems (3.5-3.8) If 2 lines in a plane are cut by a transversal so that a pair of alternate exterior angles is congruent, then the lines are parallel. If 2 lines in a plane are cut by a transversal so that a pair of consecutive interior angles is supplementary, then the lines are parallel. If 2 lines in a plane are cut by a transversal so that a pair of alternate interior angles is congruent, then the lines are parallel.

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In a plane, if 2 lines are perpendicular to the same line, then they are parallel.
Postulates Through a point outside a line, there is exactly one line parallel to the

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Unformatted text preview: given line. • Through a point outside a line, there is exactly one line perpendicular ot the given line. Theorem • 2 lines parallel to a 3 rd line are parallel to each other. Ways to Prove 2 Lines Parallel 1. Show that a pair of corresponding angles are congruent. 2. Show that a pair of alternate interior angles are congruent. 3. Show that a pair of alternate exterior angles are congruent. 4. Show that a pair of consecutive interior angles are supplementary. 5. In a plane, show that both lines are perpendicular to a 3 rd line. 6. Show that both lines are parallel to a 3 rd line. Joke Time How do you know when it’s raining cats and dogs? When you step in a poodle! Why did the apple go out with a fig? Because it couldn’t find a date...
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## This note was uploaded on 12/01/2011 for the course MATH 105 taught by Professor Towns during the Fall '10 term at BYU.

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3-5 Proving Lines Parallel - given line. • Through a...

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