code: static public double integrate(Function1D f, double tol, double a, double b)
      {
          return integrate(f, tol, a, b, 100);
      }
docs: Numerically computes the integral of the given function
  
  @param f the function to integrate
  @param tol the precision for the desired result
  @param a the lower limit of the integral
  @param b the upper limit of the integral
  @return an approximation of the integral of
  &int;<sub>a</sub><sup>b</sup>f(x) , dx