Re: Integrate Bug

*To*: mathgroup at smc.vnet.net*Subject*: [mg100451] Re: Integrate Bug*From*: Valeri Astanoff <astanoff at gmail.com>*Date*: Thu, 4 Jun 2009 03:33:54 -0400 (EDT)*References*: <gv2jh5$97b$1@smc.vnet.net>

On 21 mai, 05:58, Ney Lemke <ney.nle... at gmail.com> wrote: > I am trying to calculate this integral that should be positive.But the > answer is 0. > > In: Integrate[(1)/(z^2 + b^2 + a^2 - 2 z b Sin[\[Theta]] - > 2 a b Cos[\[Theta]])^(1/2), {\[Theta], 0, 2 \[Pi]}, > Assumptions -> {a > 0, b > 0, z > 0}] > > Out:0 > > Anybody have notice a situation like that? > > My platform is MacOSX 10.4 and Mathematica 7. > > Best wishes, Further to my previous post, seems that one single formula suffices : F[a_, b_, z_] := (4 Sqrt[a^2 + b^2 + z^2 + 2 b Sqrt[a^2 + z^2]]* Abs[Im[EllipticK[(a^4 + b^4 + 6 b^2 z^2 + z^4 + 4 b^3 Sqrt[a^2 + z^2] + 4 b z^2 Sqrt[a^2 + z^2] + 2 a^2 (3 b^2 + z^2 + 2 b Sqrt[a^2 + z^2]))/ (a^2 - b^2 + z^2)^2]]])/Abs[a^2 - b^2 + z^2] -- V.Astanoff