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Derivative, also called derivative function value. Also known as WeChat quotient, it is an important basic concept in calculus. When the independent variable x of the function y=f(x) generates an increment δ x at the point x0, if there is a limit a in the ratio of the increment δ y of the function output value to the increment δ x of the independent variable when δ x tends to 0, then A is the derivative at x0, which is denoted as f'(x0) or df(x0)/dx.
derivative
If the function y=f(x) is differentiable at every point in the open interval, it is said that the function f(x) is differentiable in the interval. At this time, the function y=f(x) corresponds to a certain derivative value for every certain value of x in the interval, and forms a new function, which is called the derivative function of the original function y=f(x), and is abbreviated as y', f'(x), dy/dx or df(x)/dx.