Secant Method
The secant method requires two initial points x0 and x1 which are both reasonably
close to the
solution x_. Preferably the signs of y0 = f(x0) and y1 = f(x1) should be different. Once
x0 and x1
are determined the method proceeds by the following
formula:
xi+1 = xi −
xi − xi−1
yi − yi−1
