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Transcript 
3-2
Angles Formed by Parallel Lines
and Transversals
Warm Up
Identify each angle pair.
1. 1 and 3
2. 3 and 6
3. 4 and 5
4. 6 and 7
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Objective
Prove and use theorems about the
angles formed by parallel lines and a
transversal.
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Example 1: Using the Corresponding Angles
Postulate
Find each angle measure.
A. mECF
B. mDCE
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Check It Out! Example 1
Find mQRS.
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Helpful Hint
If a transversal is perpendicular to
two parallel lines, all eight angles are
congruent.
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Example 2: Finding Angle Measures
Find each angle measure.
A. mEDG
B. mBDG
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Example 3: Music Application
Find x and y in the diagram.
By the Alternate Interior Angles
Theorem, (5x + 4y)° = 55°.
By the Corresponding Angles
Postulate, (5x + 5y)° = 60°.
5x + 5y = 60
5x + 4y = 55
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Check It Out! Example 3
Find the measures of the acute angles in the
diagram.
By the Alternate Exterior Angles
Theorem, (25x + 5y)° = 125°.
By the Corresponding Angles
Postulate, (25x + 4y)° = 120°.
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Lesson Quiz
State the theorem or postulate that is related
to the measures of the angles in each pair.
Then find the unknown angle measures.
1. m1 = 120°, m2 = (60x)°
2. m2 = (75x – 30)°,
m3 = (30x + 60)°
3. m3 = (50x + 20)°, m4= (100x – 80)°
4. m3 = (45x + 30)°, m5 = (25x + 10)°
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Classwork/Homework
• Pg. 158 (1-23 all, 25, 26)
Holt McDougal Geometry
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