Tau method approximation of some integrals related to radiation field problems

A more general and unified form of the Hubbell rectangular source integral is defined as subject to γ > β > 0; a, b, p> 0; λ, μ > −1. Special cases of this integral occur in some radiation field problems. Under certain restrictions, may be expressed in terms of Appellʹs double hypergeometric functions F2 and F4. Tau method approximations of the Gauss hypergeometric function 2F1 are employed in the evaluation of this integral, and upper bound estimates on the Tau error are given.