Complementary angle is a mathematical term. When the sum of degrees of two angles is 180, the two angles are complementary. Complementary angle: 180 degrees minus the degree of this angle. Complementary angle: 90 degrees MINUS the degree of this angle. The complementary angle must consist of two acute angles, and there must be an obtuse angle or a right angle in the complementary angle. Mathematical nouns are scientific nouns that study the relationship between spatial form and quantity in the real world. The meaning of mathematical nouns is of great value to etymological research, how a mathematical noun came into being and developed, and what its meaning is.