def Rz_to_uv(R,z,delta=1.,oblate=False):
    """
    NAME:

       Rz_to_uv

    PURPOSE:

       calculate prolate or oblate confocal u and v coordinates from R,z, and delta

    INPUT:

       R - radius

       z - height

       delta= focus

       oblate= (False) if True, compute oblate confocal coordinates instead of prolate

    OUTPUT:

       (u,v)

    HISTORY:

       2012-11-27 - Written - Bovy (IAS)

       2017-10-11 - Added oblate coordinates - Bovy (UofT)

    """
    coshu, cosv= Rz_to_coshucosv(R,z,delta,oblate=oblate)
    u= sc.arccosh(coshu)
    v= sc.arccos(cosv)
    return (u,v)
NAME:

       Rz_to_uv

    PURPOSE:

       calculate prolate or oblate confocal u and v coordinates from R,z, and delta

    INPUT:

       R - radius

       z - height

       delta= focus

       oblate= (False) if True, compute oblate confocal coordinates instead of prolate

    OUTPUT:

       (u,v)

    HISTORY:

       2012-11-27 - Written - Bovy (IAS)

       2017-10-11 - Added oblate coordinates - Bovy (UofT)