(Quoted from mathematics) provided the function y = f (x) are defined in a neighborhood of the point x0, when incremental argument x [Delta] x at x0, the function to obtain a corresponding increment Δy = f (x0 + Δx ) -f (x0); if the ratio of [Delta] x and Δy limit exists when Δx → 0, called the function y = f (x) can be turned on at point x0, saying this limit as a function y = f (x) in the derivative at the point x0. Mark -to-win @ Mark java Community: so that: the function y = f (x) at the point x0 derivative f '(x0) geometric meaning: a function representing the curve (x0, f (x0)) at point P0, slope of the tangent ( geometric meaning that the derivative function curve tangent slope at this point ).
And the slope of the line is usually a straight line (horizontal) axis represents a tangent of the angle difference or the ratio of the difference between the abscissa of ordinate points to tan45 = 1, tan135 = -1 represents,
Reprinted from the original article: https://blog.csdn.net/qq_44594249/article/details/100580295