Complementary angles explained

Learn about complementary angles. I will explain what are complementary angles with examples. So first read the definition and see the examples for better understanding.

Complementary angles explained

When we talk about complementary angles we should also talk about supplementary angles. These both angles we should know i.e. complementary angles and supplementary angles. The definitions of these both angles are almost same but there is a little difference. As of know we will learn complementary angles.

Definition of complementary angles:

Any two angles we can call it as complementary angles when sum of those angles gives right angle i.e. 90°. The meaning of the definition is if we take any two angles and if we add them and if the sum is right angle then we can call them as complementary angles.


56° and 34°

17° and 73°

35° and 55°

In the above three pairs of examples, if we take any one pair and if we add we will get 90° so they are complementary angles.

Let us take first pair i.e. 56° and 34°.

Add the two angles i.e. 56° + 34° = 90°. We are getting the sum as 90° so 56° and 34° are complementary angles.

Complementary angles explained

Example problems:

The ratio of complementary angles is 5 : 13 then find the angles.


               Let the two angles be 5x° and 13x°.

               According to problem,

                                                            5x° + 13x° = 90° 

                                                            18x° = 90° 

                                                            x = 90/18 = 5

Therefore the two angles are

5x° = 5 x 5° = 25°

13x° = 13 x 5° = 65°

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