Steffensen's method
In numerical analysis, Steffensen's method is an iterative method named after Johan Frederik Steffensen for numerical root-finding that is similar to the secant method and to Newton's method. Steffensen's method achieves a quadratic order of convergence without using derivatives, whereas the more familiar Newton's method also converges quadratically, but requires derivatives and the secant method does not require derivatives but also converges less quickly than quadratically.