Mathematical complementarity means that the sum of two angles is 90 degrees. For example, an angle of 60 degrees and an angle of 30 degrees are complementary, because 60 degrees +30 degrees =90 degrees. This concept is also common in Pythagorean Theorem, because Pythagorean Theorem indicates that the angles on the right-angled sides of a triangle must be complementary.

Complementarity is not only useful in the concept of angle, but also used to describe the complementarity of two objects or two people in some aspects. For example, the shapes of two coke bottles can complement each other well, so they can be easily stacked together. Similarly, two people's hobbies may be complementary, so they can gain knowledge and contact in some aspects.

Generally speaking, complementarity is a widely used concept, which is not only used in the field of mathematics, but also useful in daily life and other disciplines. Understanding the principle of complementarity can not only help us understand the concepts of geometry, physics and other disciplines, but also help us better understand the interaction between people and things.