Asymptotic Approximations for Symmetric Elliptic Integrals

Symmetric elliptic integrals, which have been used as replacements for Legendre’s integrals in recent integral tables and computer codes, are homogeneous functions of three or four variables. When some of the variables are much larger than the others, this paper presents asymptotic approximations with error bounds. In most cases they are derived from a uniform approximation to the integrand. As an application the symmetric elliptic integrals of the first, second, and third kinds are proved to be linearly independent with respect to coefficients that are rational functions.