Warm-upName the angle pair relationships.

123

4

56

78

1 and 6 - 2 and 7 - 3 and 5 -4 and 5 - 6 and 7 - 1 and 4 -

CorrespondingAlternate ExteriorAlternate InteriorConsecutive InteriorLinearVertical

Benchmark #12!!

Wednesday, October 13, 2010

Geometry Notes3.1 - Properties of Parallel Lines

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Parallel Line Theorems

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Corresponding Angles Postulate

If two lines are parallel (and cut by a transversal), then the corresponding angles are congruent. (Postulate 3-1)

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Alternate Interior Angles Theorem

If two lines are parallel, then the alternate interior angles are congruent.

Wednesday, October 13, 2010

Alternate Exterior Angles Theorem

If two lines are parallel, then the alternate exterior angles are congruent.

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Same-Side Interior Angles Theorem

If two lines are parallel, then the consecutive interior angles are supplementary.

Also works with Same-Side Exterior Angles

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So which is which?≅ (Congruent)

•corresponding•alternate

✤interior✤exterior

•vertical

adds to 180 (supplementary)

•same-side✤interior✤exterior

•linear

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ExamplesExample 1:

Find the missing angles.

x

y75°

x=75° because it is corresponding with 75°.

y=75° because it is alternate exterior

with x.

Example 2: Solve for x.

5x-24

89

89 + 5x-24 = 180°(Consecutive angles are

Supplementary)5x + 65 = 180

5x = 115x = 23°

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How to set it up:

Decide what kind of angle relationshipDecide ≅ or _ + _ = 180Set it and Solve itCheck it

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Assignments:

Angle Pairs Worksheet

#16 p. 131 #1-13 (odd), 14-17, 19-22

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