Editing Secant method (section)

==The method==
The secant method is an iterative numerical method for finding a zero of a function {{mvar|f}}. Given two initial values {{math|''x''<sub>0</sub>}} and {{math|''x''<sub>1</sub>}}, the method proceeds according to the [[recurrence relation]]
:<math>
x_n
 = x_{n-1} - f(x_{n-1}) \frac{x_{n-1} - x_{n-2}}{f(x_{n-1}) - f(x_{n-2})}
 = \frac{x_{n-2} f(x_{n-1}) - x_{n-1} f(x_{n-2})}{f(x_{n-1}) - f(x_{n-2})}.
</math>

This is a nonlinear second-order recurrence that is well-defined given {{mvar|f}} and the two initial values {{math|''x''<sub>0</sub>}} and {{math|''x''<sub>1</sub>}}. Ideally, the initial values should be chosen close to the desired zero.