Lesson 9-3 Pages 447-451

Angles

Lesson Check 9-2

What you will learn!1. How to measure and draw angles.

2. How to classify angles as acute, right, obtuse, or straight.

PointPoint DegreeDegree

RayRay ProtractorProtractor

LineLine Acute angleAcute angle

AngleAngle Right angleRight angle

VertexVertex Obtuse angleObtuse angle

SideSide Straight angleStraight angle

What you really need to know!An angle is made up of two rays that have a common endpoint, called the vertex.

The most common unit of measure for angles is the degree. There are 360° in a circle.

Angles are measured using protractors.

S

R

W

Example 1:

Use a protractor to measure RSW.

42°

U M

Example 1B:

Find the measures of GUM, SUM, BUG.

G

S

B

U M

mGUM=120°; mSUM=32°; mBUG=60°;

G

S

B

Example 2:

Draw R having a measure of 145°.

145°R

Example 3:

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

Acute

Example 3:

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

Straight

Example 3:

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

Obtuse

Example 4:

The diagram shows the angle between the back of a chair and the seat of the chair. Classify this angle.

Obtuse

Page 449

Guided Practice

#’s 3-9

Pages 447-449 with someone at home and

study examples!

Read:

Homework: Pages 450-451

#’s 10-34 all

#’s 37-51

Practice Quiz 1 #’s 1-5Lesson Check 9-3

Page

745

Lesson 9-3

Lesson Check 9-3