An example of a trigonometric function is the sine function, which is defined as the ratio of the length of the opposite side of a right triangle to the length of the hypotenuse. The sine function is commonly denoted as sin(x), where x is the angle in radians. Another example of a trigonometric function is the cosine function, which is defined as the ratio of the length of the adjacent side of a right triangle to the length of the hypotenuse. The cosine function is commonly denoted as cos(x), where x is the angle in radians. Trigonometric functions are used in a variety of fields, including physics, engineering, and mathematics, to model periodic phenomena such as sound waves and electromagnetic waves.