Re: Something wrong with this integral (see text)

*To*: mathgroup at smc.vnet.net*Subject*: [mg44603] Re: Something wrong with this integral (see text)*From*: "RFins" <rf31415 at hotmail.com>*Date*: Mon, 17 Nov 2003 03:38:38 -0500 (EST)*References*: <boif3m$oaf$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Well if you add the integrands you get an integral of Cos[L] which is clearly NOT integrable over the positive real axis, and since integration is a linear operator that means there is indeed a problem. The first integral is actually non-integrable. regards, RF "Ihor Stealth" <stealth at gmx.net> wrote in message news:boif3m$oaf$1 at smc.vnet.net... > Hi All > > 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? > > Tnx for any help. > > Ihor > > >