def calc_radii_ratio_from_rads(radius_sep_s, radius_sep_g):
    """Calculate ratio of radii of smaller-sized star to greater-sized star.
    
    Parameters
    ----------
    radius_sep_s : float
        Radius of smaller-sized star. Unit is star-star separation distance.
    radius_sep_g : float
        Radius of greater-sized star. Unit is star-star separation distance.
    
    Returns
    -------
    radii_ratio_rad : float
        Ratio of radii of smaller-sized star to greater-sized star calculated from star radii.
        radii_ratio = radius_s / radius_g
    
    Notes
    -----
    radii_ratio = radius_sep_s / radius_sep_g
    From equations 7.8 in section 7.3 of [1]_.
    
    References
    ----------
    .. [1] Budding, 2007, Introduction to Astronomical Photometry
    
    """
    radii_ratio_rad = radius_sep_s / radius_sep_g
    return radii_ratio_rad
