Re: NIntegrate with floating point limits

*To*: mathgroup at smc.vnet.net*Subject*: [mg28887] Re: NIntegrate with floating point limits*From*: "Orestis Vantzos" <atelesforos at hotmail.com>*Date*: Thu, 17 May 2001 04:22:59 -0400 (EDT)*Organization*: National Technical University of Athens, Greece*References*: <9dtasf$f7l@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

I haven't pinned down the problem exactly yet, but it appears the problem is not in the limits but in the expression you integrate: x=1/4; NIntegrate[....,{u , 0 , .25}]; works just fine! When you use floating point value for x IN the expression you get the message. My best guess for now, is that there is a singularity involved and Mathematica can't locate it when the integrand is defined using fl.point value for x... Orestis Vantzos "Fred Simons" <f.h.simons at tue.nl> wrote in message news:9dtasf$f7l at smc.vnet.net... > Dear mathgroup, > > Can someone explain why the following integral can only be computed > numerically with exact limits and not with a floating point limit? > > x = 1/4; NIntegrate[ CosIntegral[(x - u)/x + 1] - CosIntegral[1 - (x - > u)/x], {u, 0, x}] > > returns 0.2362; > > x = N[1/4]; NIntegrate[ CosIntegral[(x - u)/x + 1] - CosIntegral[1 - (x - > u)/x], {u, 0, x}] > > returns some complaints and no result. > > In all cases I met so far, floating points limits in numerical integration > caused no problems. > > Many thanks in advance, > > Fred Simons > > >