Tangent, the name of the tangent function of the mathematical trigonometric function, abbreviated as TG (before TG (1990)), is currently Tan, which is used for computer function call.
When the vertex of an angle coincides with the origin of a plane rectangular coordinate system and the starting edge of the angle coincides with the positive direction of the X axis, the quotient obtained by dividing the ordinate of any point on the final edge of the angle by the non-zero abscissa of the point.
Definition of function: Given a number set A, apply the corresponding rule F to A, and record it as f(A) to get another number set B, that is, B=f(A). Then this relationship is called functional relationship, or function for short. The concept of function includes three elements: definition field A, value field C and corresponding rule F, among which the core is corresponding rule F, which is the essential feature of function relationship.
Function was originally translated by Li, a mathematician of Qing Dynasty in China, in his book Algebra. He translated this way because "whoever believes in this variable is the function of that variable", that is, the function means that one quantity changes with another quantity, or that one quantity contains another quantity.