Copyright © by Holt, Rinehart and Winston. All Rights Reserved. Definitions Parallel Lines Two...

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DefinitionsParallel LinesTwo lines are parallel lines if they lie in the same plane and do not intersect.

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DefinitionsPerpendicular LinesTwo lines are perpendicular lines if they intersect to form a right angle.

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DefinitionsSkew LinesTwo lines are skew lines if they do not lie in the same plane. Skew lines never intersect.

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DefinitionsConverseThe converse of an if-then statement is the statement formed by switching the hypothesis and the conclusion. Here is an example.

Statement: If two segments are congruent, then the two segments have the same length.

Converse: If two segments have the same length, then the two segments are congruent.

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Theorem 3.1All right angles are congruent.

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Theorem 3.2• If two lines are perpendicular, then

they intersect to form four right angles.

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Theorem 3.3If two lines intersect to form adjacent congruent angles, then the lines are perpendicular.

Converse:If two lines are perpendicular, then they form congruent adjacent angles.

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Theorem 3.4If two sides of adjacent acute angles are perpendicular, then the angles are complementary.

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Section 3.4 & 3.5 Parallel lines and Transversals

3.3 Parallel Lines and Transversals

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3.3 Parallel Lines and Transversals

DefinitionsTransversal:Is a line, ray or segment that intersects two or more coplanar lines, rays or segments each at a different point

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3.3 Parallel Lines and Transversals

DefinitionsAlternate Interior AnglesAre two nonadjacent interior angles that lie on opposite sides of a transversal

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3.3 Parallel Lines and Transversals

DefinitionsAlternate Exterior Angles Are two nonadjacent exterior angles that lie on opposite sides of a transversal

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3.3 Parallel Lines and Transversals

Definitions

Same-Side Interior Angles Are interior angles that lie on the same side of a transversal

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3.3 Parallel Lines and Transversals

DefinitionsCorresponding Angles Are two nonadjacent angles, one interior and one exterior, that lie on the same side of a transversal

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3.3 Parallel Lines and Transversals

1) Identify pairs of angles.

Corresponding angles

Alternate interior angles

Same-side interior angles

Alternate exterior angles

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3.3 Parallel Lines and Transversals

Theorems, Postulates, & DefinitionsCorresponding Angles Postulate 8: If two parallel lines are cut by a transversal, then corresponding angles are congruent.

.

corresponding angles

2 3

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3.3 Parallel Lines and Transversals

Theorems, Postulates, & DefinitionsAlternate Interior Angles Theorem 3.3.3: If two lines cut by a transversal are parallel, then alternate interior angles are congruent.alternate interior angles

1 3

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3.3 Parallel Lines and Transversals

Theorems, Postulates, & DefinitionsAlternate Exterior Angles Theorem 3.3.4: If two lines cut by a transversal are parallel, then alternate exterior angles are congruent.alternate exterior angles

2 5

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3.3 Parallel Lines and Transversals

Theorems, Postulates, & Definitions

Same-Side Interior Angles Theorem 3.3.5: If two lines cut by a transversal are parallel, then same-side interior angles are supplementary.same-side interior angles

1 + 4 = 180

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Theorem 3.12In a plane, if two lines are perpendicular to the same line, then they are parallel to each other.

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3.3 Parallel Lines and Transversals

2) Find angle measures formed by parallel lines

and transversals.

m || n and m1 = 135°.

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3.3 Parallel Lines and Transversals

3) Given m || n and transversal t

Prove: 1 3

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