In Mathematics, the complementary angles are the set of two angles such that their sum is equal to 90 degree. For example, 30 degree and 60 degree are complementary to each other as their sum is equal to 90 degree. Two angles are complementary angles if their sum is 90 degrees. For example, if one angle is x^o, then the second angle will be (90-x)^o. If the sum of two angles is one right angle or 90 degree, then one angle is said to be complementary of the other. The topic discussed in detail is the Trigonometric Ratios of Complementary Angles.