在数值分析中，割线法是一个求根算法，该方法用一系列割线的根来近似代替函数f的根。

割线法由以下的递推关系定义：

从上式中可以看出，割线法需要两个初始值x₀和x₁，它们离函数的根越近越好。

In numerical analysis, the secant method is a root-finding algorithm that uses a succession of roots of secant lines to better approximate a root of a function f. The secant method can be thought of as a finite difference approximation of Newton's method. However, the method was developed independently of Newton's method, and predates it by over 3,000 years.