Re: Something wrong with this integral (see text)

*To*: mathgroup at smc.vnet.net*Subject*: [mg44436] Re: Something wrong with this integral (see text)*From*: "David W. Cantrell" <DWCantrell at sigmaxi.org>*Date*: Sun, 9 Nov 2003 06:01:24 -0500 (EST)*References*: <boif3m$oaf$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

"Ihor Stealth" <stealth at gmx.net> wrote: > I calculated two expressions: > > FullSimplify[Integrate[(-L^2)/(L^2 + 1)*Cos[L], {L,0, Infinity}]] > > and > > FullSimplify[Integrate[(-1)/(L^2 + 1)*Cos[L], {L,0, Infinity}]] > > They gave the same result, but in the first expression when we take > L->Infinity, it's impossible to take integral, but MAthematica CAN do > that. > > What the explanation of this? This question was posted, separately, by Ihor to sci.math, where it has already been thoroughly answered. In short, at least in version 5: The two integrals do not give the same result, and for the first integral, Mathematica says "Unable to check convergence." David Cantrell