Define
to be the solution of the differential equation
that is infinitely differentiable on the interval
, including
. Then

all functions taking their principal values, with
,
corresponding to
, respectively.
As
through positive real values
uniformly for
in all cases, where
and
are the Airy
functions (§9.2).
In the following formulas for the coefficients
,
,
, and
,
,
are the constants defined in
§9.7(i), and
,
are the polynomials in
of degree
defined in §10.41(ii).
The function
given by (10.20.2) and
(10.20.3) can be continued analytically to the
-plane cut
along the negative real axis. Corresponding points of the mapping are shown in
Figures 10.20.1 and 10.20.2.
The equations of the curved boundaries
and
in the
-plane are given parametrically by
respectively.
The curves
and
in the
-plane are the inverse maps of
the line segments
respectively. They are given parametrically by
where
is the positive root of the equation
. The points
where these curves intersect the
imaginary axis are
, where
The eye-shaped closed domain in the uncut
-plane that is bounded by
and
is denoted by
; see Figure
10.20.3.
As
through positive real values the expansions
(10.20.4)–(10.20.9) apply uniformly for
, the coefficients
,
,
, and
, being the analytic continuations of the
functions defined in §10.20(i) when
is real.
For proofs of the above results and for error bounds and extensions of the
regions of validity see Olver (1997b, pp. 419–425). For extensions
to complex
see Olver (1954). For resurgence properties of the
coefficients (§2.7(ii)) see Howls and Olde Daalhuis (1999). For further results
see Dunster (2001a), Wang and Wong (2002), and Paris (2004).