## Introduction

In this lesson, we will learn how to find measurements of angles without having to use protractors or any other tool. You see, you can always find the measurement of an angle as long as you know the following terms:Key Terms:

- Alternate Interior Angles
- Alternate Exterior Angles
- Corresponding Angles
- Vertical Angles
- Supplementary Angles
- Complementary Angles

*Note: You can learn in detail about these in the 7th Grade Unit*

## Measurement of Angles

The above is an example of a Transversal. We already know that one of the angles is 110 degrees. In order to find the other angle measurements, we need to keep in mind that the angles will

**always**add up to 180 degrees. Therefore, is we want to know the measurement of the angle directly opposite of the 110 degree angle, all we have to do is subtract 180 and 110 to get 70 degrees. That means the measurement of the opposite angle is 70 degrees!

Now taht we know the measurement of two angles directly opposite of each other, it will be really easy to find the other measurements!

The angle directly underneath the 110 degree angle is the next measurement. To find this we know that the total is 180 so if we subtract we get 70. Then comes the angle underneath the 70 degree angle. Once again, it is going to total an exact 180 degrees. So, if we subtract 180 and 70 we get 110. Notice that there is a pattern. There are only

**2 different measurements**.So as you can see it isn't really hard to find the measurements of the angles as long as you know just one of the measurements!

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