Hm, the things are not as simple as I originaly thought. Your ?g1543 seems to be a dummy variable, which is used by Maxima. Do not know how to support it in Sage.
This is our example 3 in Maxima Maxima 5.21.1 http://maxima.sourceforge.net using Lisp CLISP 2.44.1 (2008-02-23) 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) eq1: 'diff(x1(t),t) = -3*(x2(t)^2-1); (%o2) 'diff(x1(t),t,1) = -3*(x2(t)^2-1) (%i3) eq2: 'diff(x2(t),t) = 1; (%o3) 'diff(x2(t),t,1) = 1 (%i4) desolve([eq1,eq2],[x1(t),x2(t)]); (%o4) [x1(t) = 'ilt(-((3*'laplace(x2(t)^2,t,?g21841)-x1(0))*?g21841-3) /?g21841^2,?g21841,t),x2(t) = t+x2(0)] (%i5) Robert On 27 srp, 14:05, "ma...@mendelu.cz" <ma...@mendelu.cz> wrote: > Both desolve_system and desolve_laplace use Maxima's function desolve. > Desolve_laplace has been updated in 2009, but desolve_system not. I > believe that desolve_system could be improved in the same way as > desolve_laplace. Please, make a trac report and put me (robert.marik) > into Cc field. Thanks > > Robert > > On 26 srp, 23:25, Ryan Hinton <iob...@email.com> wrote: > > > I am having trouble trying to use desolve_system. Am I doing > > something wrong? If not, I can create trac tickets for these errors. > > > 1. If I make the reference manual example easier, I get an exception: > > > sage: t = var('t') > > sage: x = function('x', t) > > sage: de1 = diff(x,t) + 1 == 0 > > sage: desolve_system([de1], [x]) > > ... > > TypeError: unable to make sense of Maxima expression '(x(t)=x(0)-t) > > [1]' in Sage > > > 2. Initial conditions are apparently ignored. > > > sage: t = var('t') > > sage: epsilon = var('epsilon') > > sage: x1 = function('x1', t) > > sage: x2 = function('x2', t) > > sage: de1 = diff(x1,t) == epsilon > > sage: de2 = diff(x2,t) == -2 > > sage: desolve_system([de1, de2], [x1, x2], ivar=t) > > [x1(t) == epsilon*t + x1(0), x2(t) == -2*t + x2(0)] > > sage: desolve_system([de1, de2], [x1, x2], ics=[1,1], ivar=t) > > [x1(t) == epsilon*t + x1(0), x2(t) == -2*t + x2(0)] > > > 3. Making the example nonlinear, I get a different exception. > > > sage: t = var('t') > > sage: x1 = function('x1', t) > > sage: x2 = function('x2', t) > > sage: de1 = (diff(x1,t) == -3*(x2^2-1)) > > sage: de2 = (diff(x2,t) == 1) > > sage: desolve_system([de1, de2], [x1, x2], ivar=t) > > ... > > TypeError: unable to make sense of Maxima expression 'x1(t)=ilt(- > > ((3*laplace(x2(t)^2,t,?g1543)-x1(0))*?g1543-3)/?g1543^2,?g1543,t)' in > > Sage > > > In the process of putting in my full, complicated example, I found the > > bug that produced yet another, confusing exception. :-) > > > Any guidance or suggestions are appreciated. Thanks! > > > - Ryan -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
