cubic_secant

cubic_secant
  Use the secant method to search for a root of the cubic function.

  F(1) = -1
  F(2) = 5

  After 7 iterations:
  F(1.32472) = -3.22853e-13

  it <= itmax?  true
  |a-b| <= xtol?  true
  |f(b)| <= ftol?  true
diary hump_secant.txt