Lesson 18 — Activity 1: Different Types of Angles

Getting Ready

This first activity will introduce you to the different types of angles.

You can find examples of angles in everyday life. The corner of a fridge is a right angle. There is an acute angle between your keyboard on the computer and the desk it sits on. When you lean back in your chair, the back of the chair and your desktop are at an obtuse angle. When you open up a book and lay it flat, you get a straight angle.

Think about This:

Find examples of angles in your classroom or at home. You will be amazed at how many you can find!

This image shows a straight angle.
Image courtesy of www.imagesgoogle.com 

An angle is the difference in direction between two lines.

Look at this image.

Angle Image 1

As you can see from looking at the image, the difference in directions between the two lines is 40°.

A degree is a unit used to measure angles. A circle has 360 degrees in it, and a right angle has 90 degrees in it.

Besides a right angle (90°), there are three other types of angles that you will be working with.

They are:

Acute angles — any angle between 0° and 90°

This image shows an acute angle.

Obtuse angles — any angle greater than 90° but less than 180°

This image shows an obtuse angle.

Straight angles — any angle that is 180° or a straight line

This image shows a straight angle.

Digging Deeper

Click here to try this game on identifying different types of angles.