where
(
) is a real or complex constant, and
In (19.16.1) and (19.16.2),
except that one or more of
may be 0 when the corresponding integral converges. In (19.16.2) the
Cauchy principal value is taken when
is real and negative. In
(19.16.3)
,
,
. It
should be noted that the integrals (19.16.1)–(19.16.3)
have been normalized so that
.
A fourth integral that is symmetric in only two variables is defined by
with the same conditions on
,
,
as for (19.16.1), but now
.
Just as the elementary function
(§19.2(iv)) is
the degenerate case
and
is a degenerate case of
, so is
a
degenerate case of the hyperelliptic integral,
All elliptic integrals of the form (19.2.3) and many multiple integrals, including (19.16.3), are special cases of a multivariate hypergeometric function
which is homogeneous and of degree
in the
’s, and unchanged when the
same permutation is applied to both sets of subscripts
. Thus
is symmetric in the variables
and
if the parameters
and
are equal. The
-function
is often used to make a unified statement of a property of several elliptic
integrals. Before 1969
was denoted by
.

where
is the beta function (§5.12) and
For further information, especially representation of the
-function as a
Dirichlet average, see Carlson (1977b).
is an elliptic integral iff the
’s
are distinct and exactly four of the parameters
are
half-odd-integers, the rest are integers, and none of
,
,
is zero
or a negative integer. The only cases that are integrals of the first kind are
the four in which each of
and
is either
or 1 and each
is
. The only cases that are integrals of the third kind are
those in which at least one
is a positive integer. All other elliptic
cases are integrals of the second kind.
(Note that
is not an elliptic integral.)