The definition of differential in mathematics: from the function B=f(A), two groups of numbers A and B are obtained. In A, when dx approaches itself, the limit of the function at dx is called the differential of the function at dx, and the central idea of the differential is infinite division. Differential is the linear main part of function change. One of the basic concepts of calculus.

Extended data:

Differential application

1, normal

The normal of a point on the curve and the tangent of that point are perpendicular to each other, and the slope of the tangent can be obtained by differentiation, and naturally the slope of the normal can also be obtained.

Suppose the image of function y=f(x) is a curve with a point (x 1, y 1), then according to the solution of tangent slope, we can get the slope m of tangent at this point:

M = the value of dy/dx at (x 1, y 1).

2. increasing function sum subtraction function.

Differential is an effective method to distinguish whether a function (in a specified domain) is a increasing function or a subtraction function.

Identification method: compare dy/dx with 0. When dy/dx is greater than 0, it means that when dx increases to a positive value, dy increases to a positive value, so the function is increasing function; When dy/dx is less than 0, it means that when dx increases to a positive value, dy increases to a negative value, so the function is a subtraction function.