From: SourceForge.net <no...@so...> - 2012-01-10 07:08:23
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Bugs item #3471545, was opened at 2012-01-09 14:49 Message generated for change (Comment added) made by aleksasd You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3471545&group_id=4933 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Share Libraries Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Richard Hennessy (richhennessy610) Assigned to: Nobody/Anonymous (nobody) Summary: integrate gives complex area Initial Comment: In evaluating integrate(exp(-signum(x-2)*x^3),x,-2,3); maxima gives complex result. Integrand is real valued and has well defined area under the curve. I would expect Maxima to give real number for result. (%i2) load(abs_integrate); (%o2) C:/Maxima-5.25.1/share/maxima/5.25.1/share/contrib/integration/abs_integrate.mac (%i3) display2d:false; (%o3) false (%i4) integrate(exp(-signum(x-2)*x^3),x,-2,3); (%o4) gamma_incomplete(1/3,-8)/3-gamma_incomplete(1/3,27)/3 (%i5) rectform(float(%)); (%o5) -239.7616342762335*%i-137.5334645791589 (%i6) build_info(); Maxima version: 5.25.1 Maxima build date: 10:2 9/6/2011 Host type: i686-pc-mingw32 Lisp implementation type: GNU Common Lisp (GCL) Lisp implementation version: GCL 2.6.8 (%o6) "" (%i7) ---------------------------------------------------------------------- Comment By: Aleksas (aleksasd) Date: 2012-01-09 23:08 Message: (%i1) f:exp(-signum(x-2)*x^3)$ By properties of definite integral integrate(f,x,-2,3)=integrate(f,x,-2,0)+integrate(f,x,0,2)+integrate(f,x,2,3) (%i2) integrate(f,x,-2,0)+integrate(f,x,0,2)+integrate(f,x,2,3)$ float(%), expand; sol:realpart(%); (%o3) 277.7458676930253-4.263256414560601*10^-14*%i (%o4) 277.7458676930253 (%i5) /* test*/ first(quad_qags(exp(-signum(x-2)*x^3),x,-2,3)); (%o5) 277.7458676961945 Aleksas D. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3471545&group_id=4933 |