In Mathematics, the trigonometric functions (also called circular functions) are functions of angles. They were originally used to relate the angles of a triangle to the lengths of the sides of a triangle. Trigonometric functions are useful in the study of triangles and also in many different phenomena in real life.

The most familiar trigonometric functions are sine and cosine functions. In this unit, you will be studying the properties of these functions in detail, including their graphs and some practical applications of the two basic trigonometric functions.