Download Parallel Lines and Transversals Angle Measure Relationships

3-2
Angles Formed by Parallel Lines
and Transversals
Bellringer:
Identify each angle pair.
1. ∠1 and ∠3
corr. ∠s
2. ∠3 and ∠6
alt. int. ∠s
3. ∠4 and ∠5
alt. ext. ∠s
4. ∠6 and ∠7
same-side int ∠s
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
Bellringer: Copy this picture into your
notes.
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Corresponding angles are congruent.
Alternate interior angles are congruent.
Alternate exterior angles are congruent.
Same side interior angles are supplementary.
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 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
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
Check It Out! Example 2
Find m∠
∠ABD.
Holt McDougal Geometry
3-2
Angles Formed by Parallel Lines
and Transversals
Practice Problems
Find x and then the unknown angle measures.
1. m∠1 = 120°, m∠2 = (60x)°
2. m∠2 = (75x – 30)°,
m∠3 = (30x + 60)°
3. m∠3 = (2x + 1)°,
m∠5 = (3x + 9)°
Holt McDougal Geometry