2. Main Idea and New Vocabulary Key Concept: Types of Angles
Example 1: Name Angles
Key Concept: Pairs of Angles
Example 2: Real-World Example
Example 3: Find a Missing Angle Measure
Lesson Menu

3. Classify angles and identify vertical and adjacent angles.
congruent
vertex
acute angle
right angle
obtuse angle
straight angle
vertical angles
adjacent angles
Main Idea/Vocabulary

4. Key Concept

5. Since the angle is less than 90°, it is an acute angle.
Name Angles
Name the angle below in four ways. Then classify it as acute, right, obtuse, or straight.
• Use the vertex as the middle letter and a point from each side, FGH or HGF.
• Use the vertex only, G.
• Use a number, 2.
Since the angle is less than 90°, it is an acute angle.
Example 1

6. Answer: FGH, HGF, G, 2; acute
Name Angles
Answer: FGH, HGF, G, 2; acute
Example 1

7. Name the angle below in two ways
Name the angle below in two ways. Then classify it as acute, right, obtuse, or straight.
A. JKL, K; acute
B. LKJ, K; right
C. JKL, K; obtuse
D. LKJ, J; obtuse
Example 1 CYP

8. Key Concept 2

9. 4 and 5 are adjacent angles because they share a common side.
SEWING Identify a pair of vertical angles and adjacent angles in the diagram. Justify your response.
Answer: 3 and 5 are vertical angles because they are opposite angles formed by intersecting lines.
4 and 5 are adjacent angles because they share a common side.
Example 2

10. A. vertical: 5 and 7 adjacent: 5 and 8
HIKING Identify a pair of vertical angles and adjacent angles in the diagram of the hiking trails.
A. vertical: 5 and 7 adjacent: 5 and 8
B. vertical: 5 and 8 adjacent: 6 and 7
C. vertical: 6 and 7 adjacent: 5 and 8
D. vertical: 6 and 7 adjacent: 7 and 8
Example 2 CYP

11. Find a Missing Angle Measure
What is the value of y in the figure below?
The angle labeled y and the angle labeled 60 are vertical angles. Since vertical angles are congruent, the value of y is 60.
Answer: 60°
Example 3

12. What is the value of x in the figure below?
C. 104°
D. 180°
Example 3 CYP