NIntegrate with floating point limits

*To*: mathgroup at smc.vnet.net*Subject*: [mg28864] NIntegrate with floating point limits*From*: "Fred Simons" <f.h.simons at tue.nl>*Date*: Wed, 16 May 2001 03:28:11 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

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