(Never Mind? Can't duplicate result!) Re: Can

*To*: mathgroup at smc.vnet.net*Subject*: [mg81880] (Never Mind? Can't duplicate result!) Re: [mg81827] Can*From*: "W. Craig Carter" <ccarter at mit.edu>*Date*: Fri, 5 Oct 2007 04:59:30 -0400 (EDT)*References*: <200710040827.EAA22349@smc.vnet.net>

Dear Mathgroup, I've tried again to duplicate the results below with a fresh kernal, and I can't. I am now getting a sensible result. Apologies to anyone who might have put time into this. Craig On Thu, 4 Oct 2007, W. Craig Carter wrote: > Date: Thu, 4 Oct 2007 04:27:21 -0400 (EDT) > From: W. Craig Carter <ccarter at MIT.EDU> > To: mathgroup at smc.vnet.net > Subject: [mg81827] Can Integrate[expr,{x,a,b}] give an incorrect result? > > > I believe I am getting an incorrect result from a definite > integration: > > InputForm[integrand] is > (R*(R - rho*Cos[alpha - t]))/(3*(R^2 + rho^2 + (z - zeta)^2 - 2*R*rho*Cos[alpha - t])^3) > > InputForm[assumptions] is > {R > 0, L > 0, rho > 0, Element[zeta, Reals], Element[z, Reals], alpha > 0} > > Integrate[integrand,{t,0,2Pi},Assumptions->assumptions] > returns 0 > > But compare this to: > (visually integrate...) > Plot[integrand/.{R -> 1, rho -> 1.1, zeta -> 0, alpha -> 0, z -> 1.2},{t,0,2 Pi},PlotRange->All] > > (numerically integrate...) > Plot[NIntegrate[integrand/.{{R -> 1, rho -> 1.1, zeta -> 0, alpha -> 0, z -> 1.2},{t,0,tau}],{tau,0,2Pi}, PlotRange->All] > > > Something isn't adding up?? > > Thanks, WCC > >

**References**:**Can Integrate[expr,{x,a,b}] give an incorrect result?***From:*"W. Craig Carter" <ccarter@mit.edu>