From: SourceForge.net <noreply@so...>  20120414 17:07:16

Bugs item #3517785, was opened at 20120414 10:07 Message generated for change (Tracker Item Submitted) made by mjorlitzky You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3517785&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: Lisp Core  Integration Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Michael Orlitzky (mjorlitzky) Assigned to: Nobody/Anonymous (nobody) Summary: Wrong sign in exponential integral Initial Comment: Laurent Decreusefond reported this on the sagesupport mailing list. The function is positive, yet a negative result is returned from integrate(). I believe the correct result is +1. Maxima 5.27.0 http://maxima.sourceforge.net using Lisp ECL 12.2.1 Distributed under the GNU Public License. See the file COPYING. Dedicated to the memory of William Schelter. The function bug_report() provides bug reporting information. (%i1) display2d: false; (%o1) false (%i2) f: 1/(%e^(2*t)*sqrt(11/%e^(2*t))); (%o2) %e^(2*t)/sqrt(1%e^(2*t)) (%i3) integrate(f, t, 0, inf); (%o3) 1  You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3517785&group_id=4933 
From: SourceForge.net <noreply@so...>  20120502 04:25:21

Bugs item #3517785, was opened at 20120414 10:07 Message generated for change (Comment added) made by rtoy You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3517785&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: Lisp Core  Integration Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Michael Orlitzky (mjorlitzky) Assigned to: Nobody/Anonymous (nobody) Summary: Wrong sign in exponential integral Initial Comment: Laurent Decreusefond reported this on the sagesupport mailing list. The function is positive, yet a negative result is returned from integrate(). I believe the correct result is +1. Maxima 5.27.0 http://maxima.sourceforge.net using Lisp ECL 12.2.1 Distributed under the GNU Public License. See the file COPYING. Dedicated to the memory of William Schelter. The function bug_report() provides bug reporting information. (%i1) display2d: false; (%o1) false (%i2) f: 1/(%e^(2*t)*sqrt(11/%e^(2*t))); (%o2) %e^(2*t)/sqrt(1%e^(2*t)) (%i3) integrate(f, t, 0, inf); (%o3) 1  >Comment By: Raymond Toy (rtoy) Date: 20120501 21:25 Message: To evaluate this definite integral, maxima recognizes this as f(exp(k*x)) and uses the substitution s + 1 = exp(k*x). This should give integrate(1/sqrt(s),s,0,1)/(2) for this integral, which maxima evaluates to 1 correctly. However, internally, maxima gets confused and wants to do integrate(%i/2/sqrt(s),s,0,1) which is 1. Hence the incorrect answer is produced. One obvious solution is to change the substitution to be 1s=exp(k*x) when k < 0. If this is done, maxima produces the correct answer. But the original substitution is correct too and I don't know where maxima goes wrong.  You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3517785&group_id=4933 