Page 88 - Math Course 1 (Book 2)

Geometry: Angles

right angle
A right angle is equal to 90°. Let’s Begin

Name right angle

Measure m ∠A = 90 Measure and Classify Angles

This symbol Examples
means a 90 o
Model angle
A. Measure ∠TYV and classify it as right, acute, or
obtuse.
A

acute angle
An acute angle is less than 90°.

Name acute angle

Measure m ∠B < 90

m∠TYV = 90, so ∠TYV is a right
Model Answer
angle.

B B. Measure ∠WYT and classify it as right, acute, or
obtuse.
obtuse angle
An obtuse angle is more than 90° but less than
180°.

Name obtuse angle

Measure 180 > m ∠C > 90

Use protractor to
f nd m∠WYT =130
Model
Answer 180 > m ∠WYT > 90, so ∠WYT is
an obtuse angle.
C

Key Concept Angle
Words An angle is formed by two non-collinear rays that have a common endpoint
Symbols Model

→
∠A side AB
∠BAC B
∠CAB Vertex A A 4
∠4 →
side AC C

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