Main Idea and New Vocabulary

NGSSS

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

Five-Minute Check

• Classify angles and identify vertical and adjacent angles.

• congruent

• vertex

• acute angle

• right angle

• obtuse angle

• straight angle

• vertical angles

• adjacent angles

MA.8.G.2.2 Classify and determine the measure of angles, including angles created when parallel lines are cut by transversals.

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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.

Name Angles

Answer: FGH, HGF, G, 2; acute

A. JKL, K; acute

B. LKJ, K; right

C. JKL, K; obtuse

D. LKJ, J; obtuse

Name the angle below in two ways. Then classify it as acute, right, obtuse, or straight.

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SEWING Identify a pair of vertical angles and adjacent angles in the diagram. Justify your response.

Answer: 3 and 5 are vertical angles becausethey are opposite angles formed byintersecting lines.

4 and 5 are adjacent angles becausethey share a common side.

A. vertical: 5 and 7adjacent: 5 and 8

B. vertical: 5 and 8adjacent: 6 and 7

C. vertical: 6 and 7adjacent: 5 and 8

D. vertical: 6 and 7adjacent: 7 and 8

HIKING Identify a pair of vertical angles and adjacent angles in the diagram of the hiking trails.

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°

A. 14°

B. 76°

C. 104°

D. 180°

What is the value of x in the figure below?

A. acute

B. right

C. obtuse

D. straight

Classify the angle as acute, right, obtuse, or straight.

A. acute

B. right

C. obtuse

D. straight

Classify the angle as acute, right, obtuse, or straight.

A. acute

B. right

C. obtuse

D. straight

Classify the angle as acute, right, obtuse, or straight.

A. 1 and 2

B. 1 and 3

C. 2 and 3

D. 1 and 4

Identify a pair of vertical angles.

A. true

B. false

Tell whether the following statement is true or false. A straight angle has a measure of 180°.

A. 1 and 3

B. 2 and 3

C. 2 and 4

D. none of the above

Which of the angles shown in the diagram are adjacent?

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