secant method for finding roots

Write a function m-file called secant.m which uses this method to find the root of a given function between points a and b. The function should stop iterating when x_n and x_n-1 have the same value, to e decimal places.

I understand that The function should have 4 arguments: a function f, the points a and b and a number e. I am unsure how to write it given that I have constants instead of number values for the two points.

[Geoff Hayes]

Sey - when you say that you are unsure how to write it given that I have constants instead of number values, do you mean the variables (input parameters) to your function are what is causing the problem? And if so, why? From your description, the function signature would be

 function [root] = secant(fun,a,b,epsilon)

How would you implement the secant method given its description found at http://en.wikipedia.org/wiki/Secant_method?