def curvature(x, dfunc, d2func, *args, **kwargs):
    """ Curvature of function f''/(1+f'^2)^3/2
          x         independent variable
          dfunc     first derivative of function f: f'
          d2func    second derivative of function f: f''
          args      arguments for dfunc and d2func
          kwargs    keyword arguments for dfunc and d2func
    """
    return d2func(x, *args, **kwargs)/(1.+dfunc(x, *args, **kwargs)**2)**1.5