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.

brief introduction

Let the function y = f(x) be defined in the neighborhood of X, and both X and x+δ x are in this interval. If the increment of the function Δ y = f(x+Δ x)-f (x) can be expressed as Δ y = a Δ x+o (Δ x) (where a is a constant that does not change with Δ x, but a can change with x), and o (Δ x) is infinitely less than Δ x (note: o is pronounced as Omicron, Greek letter), then the function f (x) is called.

Aδx is called the differential of the function corresponding to the dependent variable increment δy at point X, and it is denoted as dy, that is, Dy = A δ x. The differential of the function is the main part of the function increment and is a linear function of δ x, so the differential of the function is the linear main part of the function increment (δ x→ 0).