The term Sine and Cosine are two of the most important trigonometric functions. They are ratios of the sides of a right triangle to its hypotenuse, and are used to calculate angles and distances in many mathematical problems. The sine of an angle is the ratio of the length of the opposite side to the length of the hypotenuse, while the cosine is the ratio of the adjacent side to the hypotenuse. Both sine and cosine are essential for solving problems involving triangles, circles, and other geometric shapes.