With the notation of §12.14(i),
Principal values on each side of these equations correspond.
For the functions
and
see §13.2(i).

For the functions
and
see
§13.14(i).
In all cases principal branches correspond at least when
.
For
see (16.2.1).
With
as in §15.2(i), and with
and
fixed,
as
and
in
. For this result see
Watson (1944, §5.7).