Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

Objective

1

2

10/29Lesson 3.2

What is the name of the angle pair, angles 1 and 2?

Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

1

2

What if the lines are parallel?

Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

Postulate or Theorem Name What it says Key Words Picture

If 2 parallel lines are cut by a transversal, then…

Corresponding Angles Postulate

…the corresponding angles are congruent.

Parallel linesTransversalCorresponding angles

HANDBOOK PAGE 15

Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

Find mQRS.

Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

m

n

1

2

34

5

7

6

8

If m<8 = 61˚, find the measures of all other numbered angles.

Example 1)

Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

m

n

1

2

34

5

7

6

8

Alternate Interior angles are ____________.

Alternate exterior angles are ____________.

Same-side interior angles are ____________.

Example 2)

Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

Alternate Interior Angles Theorem

…the alternate interior angles are congruent.

Parallel linesTransversalAlternate interior angles

Alternate Exterior Angles Theorem

…the alternate exterior angles are congruent.

Parallel linesTransversalAlternate exterior angles

Same-side Interior Angles Theorem

…the same-side interior angles are supplementary.

Parallel linesTransversalSame-side interior anglesSupplementary

Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

Find each angle measure.

A. mDCE

B. mCBG

Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

Given m3 = 3x-1 and m5 = x+5.

Find m1.

Example 3)

Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

Given m3 = 2(x-35) and m4 = x+15.

Find m5.

Example 4)

Holt Geometry

3-2 Angles Formed by Parallel Lines and Transversals

Objective

Exit Slip!

1. Let m1 = 120°, m2 = (60x)°.

a. Give the name of the angle pair that

describes <1 and <2.

b. Write and solve an equation to find the

measures of the angles.

c. Name the theorem or postulate that justifies your

solution.

2. Find m3 and m5 if m3 = (45x + 30)° and m5 = (25x + 10)° .