A trigonometric function is a mathematical function that relates the angles of a triangle to the lengths of its sides. The most common trigonometric functions are sine, cosine, and tangent, which are often used in geometry and physics to solve problems involving triangles and periodic phenomena. These functions are defined for an angle in a right triangle, where sine represents the ratio of the opposite side to the hypotenuse, cosine represents the ratio of the adjacent side to the hypotenuse, and tangent represents the ratio of the opposite side to the adjacent side. Trigonometric functions are essential in various fields, including engineering, astronomy, and computer graphics.