When
is replaced by
, (28.2.1) becomes the
modified Mathieu’s equation:
with its algebraic form
Assume first that
is real,
is positive, and
;
see §28.12(i). Write
Then from §2.7(ii) it is seen that equation (28.20.2)
has independent and unique solutions that are asymptotic to
as
in the
respective sectors
,
being an arbitrary small positive constant. It follows that
(28.20.1) has independent and unique solutions
,
such that
as
with
, and
as
with
. See §10.2(ii) for
the notation. In addition, there are unique solutions
,
that are real when
is real and have the properties
as
with
.
For other values of
,
and
the functions
,
are determined by analytic
continuation. Furthermore,
For
,