def derivative(func, x, h):
    """
    Evaluate the derivative of a function
    at point x, with step size h
    Uses the symmetric derivative

    Parameters
    ----------
    func : function
        Function to evaluate
    x : float
        Point to evaluate derivative
    h : float 
        Step size


    Returns
    -------
    retval : float
        Derivative

    """
    return (func(x+h) - func(x-h))/(2*h)