# >> K-12 >> K-12 Basics

How to Find the Difference in the Measure of Two Complementary Angles

Angles are complementary if they add up to 90 degrees. For example, the sum of a 35-degree angle and a 55-degree angle is 90 degrees; therefore, these two angles would be considered complementary. Being able to identify complementary angles is a useful skill in geometry because it allows you to determine other things about the object in question as well, such as the length of the object's sides and degree of other angles.

Instructions

- 1
  Gather the necessary information. You will need to know which two angles are complementary. You will also need to know the measurement of at least one of the complementary angles.
- 2
  Subtract the angle that you know from the number 90. For example, if one of the complementary angles is 30 degrees, subtract 30 from 90 to get 60 degrees. This difference is the measurement of the unknown angle in the complementary pair.
- 3
  Subtract the smaller angle of the complementary pair from the larger angle. Using the example from above, 60 - 30 = 30. The result obtained is the difference between the two complementary angles.

Types of Carbon Paper

How to Find Median, Mode & Outliers