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:

An angle is the difference in direction between two lines.

Look at this image.

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°

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

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