Angles

1) Name and classify angles.

2) Define complementary and supplementary angles.

3) Apply definitions of complementary and supplementary angles.

Objectives

An angle has two sides than meet a the vertex. In the angle below the sides are and These two sides intersect a the vertex of the angle which is point R.

Possible Names for this angle:

1R

SRT TRS

We do: Example 1B

How many angles are there in this diagram? Give a possible name for each of them.

The measure of an angle is usually given in degrees (later in the year we will learn that you can also measure angles in radians) . A protractor is the tool used to measure angles in degrees.

I Do: Example 2A

We do: Example 2B

You Do: Example 2C

Find the measure of each angle. Then classify each as acute, right, or obtuse.

A. WXV

B. YXZ

C. ZXW

D. YXW

We do: Example 2D

Congruent angles are angles that have the same measure. Arc marks are used to show that the two angles are congruent.

In simpler words: we can add angles.

Complementary Angles (Definition)

To be complementary the sum of the two angles must equal 90 degrees.

Supplementary Angles (Definition)

To be supplementary the sum of the two angles must equal 180 degrees.

The angles in example 1 are also called a linear pair.

Example 1

Example 2

Link to Gizmos

Find the value of each angle

We Do: Example 3B

Find the value of x.

You Do: Example 3C

We Do: Example 4B

Find the value of x.

You Do: Example 4C

Exit Slip

Given mWYZ = (2x – 5)°mXYW = (3x + 10)°

Find the value of x.