This looks similar to an open https://sourceforge.net/p/maxima/bugs/3528/ where abs_integrate breaks integrate(sqrt(1+2*sin(x)^2), x);
On Wed, Mar 20, 2019 at 12:58 PM <dimp...@gmail.com> wrote: > > On Wed, Mar 20, 2019 at 05:36:59AM -0700, mmarco wrote: > > I am trying to pinpoint the following bug: > > > > sage: integral(sqrt(1+cos(x)^2),x) > > -1/24*sin(3*x) + 1/8*sin(x) > > > > > > which is incorrect. One would think that maxima is returning a wrong > > answer, but if we ask directly to maxima, it leaves the integral as it is: > indeed, it is an elliptic integral, cannot be done in elementary > functions. > > The problem comes from src/sage/interfaces/maxima_lib.py > loading abs_integrate: > > sage --maxima > ;;; Loading #P"/mnt/opt/Sage/sage-dev/local/lib/ecl/sb-bsd-sockets.fas" > ;;; Loading #P"/mnt/opt/Sage/sage-dev/local/lib/ecl/sockets.fas" > ;;; Loading #P"/mnt/opt/Sage/sage-dev/local/lib/ecl/defsystem.fas" > ;;; Loading #P"/mnt/opt/Sage/sage-dev/local/lib/ecl/cmp.fas" > Maxima 5.41.0 http://maxima.sourceforge.net > using Lisp ECL 16.1.2 > 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) load(abs_integrate); > ARRSTORE: use_fast_arrays=false; allocate a new property hash table for > $INTABLE2 > (%o1) > /mnt/opt/Sage/sage-dev/local/share/maxima/5.41.0/share/contrib/integrati\ > on/abs_integrate.mac > (%i3) display2d : false; > (%o3) false > (%i4) integrate(sqrt(1+cos(x)^2),x); > > (%o4) ((2*sin(3*x)+6*sin(x))*false-sin(3*x)+3*sin(x))/24 > > Which does not make much sense, and apparently Sage gets the bit of it > after "false"... > > Dima > > > > sage: f = sqrt(1+cos(x)^2) > > sage: maxima.integrate(f._maxima_(),x) > > 'integrate(sqrt(cos(_SAGE_VAR_x)^2+1),_SAGE_VAR_x) > > > > which is the same result we get with sympy and fricas, and even by maxima > > itself: > > > > Maxima 5.41.0 http://maxima.sourceforge.net > > using Lisp ECL 16.1.2 > > 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) integrate(sqrt(1+cos(x)^2),x); > > / > > [ 2 > > (%o1) I sqrt(cos (x) + 1) dx > > ] > > / > > > > So something strange is going on when we call maxima internally to compute > > that integral. I have tried to trace it, but I got lost in the > > intrincancies of the maxima interface. > > > > Does somebody know what exactly is causing this discrepancy? > > > > -- > > You received this message because you are subscribed to the Google Groups > > "sage-devel" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to sage-devel+unsubscr...@googlegroups.com. > > To post to this group, send email to sage-devel@googlegroups.com. > > Visit this group at https://groups.google.com/group/sage-devel. > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
