def D_rvmu(r: float, v: float, mu: float) -> float:
    """
    D = r * v * v / mu

    :param r: radius vector
    :type r: float
    :param v: velocity
    :type v: float
    :param mu: G * (m1 + m2)
    :type mu: float
    :return: D
    :rtype: float
    """
    return r * v * v / mu