Trig Calc is a branch of mathematics that deals with the study of triangles and their properties. It is also known as trigonometry, and it involves the use of angles, sides, and other geometric shapes to solve problems. The term COS is an abbreviation for cosine, which is one of the three main functions used in trigonometry. Cosine is used to calculate the ratio of the side adjacent to an angle in a right triangle to the hypotenuse.