Express the meaning of trigonometric function, tan is tangent function, y = tan x, which means that y is the ratio of the length of the opposite side to the length of the adjacent side in a right triangle with an acute angle of x degrees. Y = sinx, which is a sine function. Y is the ratio of the length of the opposite side to the length of the hypotenuse of a right triangle with an acute angle of x degrees. Others are cosine function cosx and cotangent function COX.