2. Key Concept: Transversals and Angles Example 1: Classify Relationships
Main Idea
New Vocabulary
Key Concept: Transversals and Angles
Example 1: Classify Relationships
Example 2: Classify Relationships
Example 3: Find an Angle Measure
Example 4: Find the Missing Measures
Lesson Menu

3. Identify relationships of angles formed by two parallel lines cut by a transversal.
Main Idea/Vocabulary

4. alternate interior angles alternate exterior angles
perpendicular lines
parallel lines
transversal
interior angles
exterior angles
alternate interior angles
alternate exterior angles
corresponding angles
Main Idea/Vocabulary

5. Key Concept

6. Classify Relationships
Classify 3 and 7 as alternate interior, alternate exterior, or corresponding angles.
3 and 7 are in the same position on the two lines.
Answer: They are corresponding angles.
Example 1

7. Classify 4 and 6 as alternate interior, alternate exterior, or corresponding angles.
A. alternate interior
B. alternate exterior
C. corresponding
Example 1 CYP

8. Classify Relationships
Classify 2 and 8 as alternate interior, alternate exterior, or corresponding angles.
2 and 8 are interior angles that lie on opposite sides of the transversal.
Answer: They are alternate interior angles.
Example 2

9. Classify 1 and 5 as alternate interior, alternate exterior, or corresponding angles.
A. alternate interior
B. alternate exterior
C. corresponding
Example 2 CYP

10. Since 6 and 7 are supplementary, the sum of their measures is 180°.
Find an Angle Measure
GATES Mr. Adams installed the gate shown. Line c is parallel to line d. If m4 = 40°, find m6 and m7. Justify your answer.
Since 4 and 6 are interior angles that lie on opposite sides of the transversal, they are alternate interior angles. Alternate interior angles are congruent. So, m6 = 40.
Since 6 and 7 are supplementary, the sum of their measures is 180°.
m7 = 180° – 40° or 140°
Example 3

11. Find an Angle Measure
Answer: m6 = 40° and m7 = 140°
Example 3

12. GATES Use the gate shown. Line c is parallel to line d
GATES Use the gate shown. Line c is parallel to line d. If m1 = 142°, find m8.
A. 38°
B. 42°
C. 52°
D. 142°
Example 3 CYP

13. Find the Missing Measures
In the figure, line a is parallel to line b, and line c is perpendicular to line d. The measure of 7 is 125°. What is the measure of 4?
7 and the sum of 5 and 4 are alternate exterior angles. So, m5 + m4 = 125.
Since m5 = 90°, m4 = 125 – 90 or 35°.
Answer: m4 = 35°
Example 4

14. In the figure, line a is parallel to line b, and line c is perpendicular to line d. The measure of 8 is 43°. What is the measure of 1?
A. 43°
B. 45°
C. 47°
D. 90°
Example 4 CYP