Hope the following is a non-trivial example: from my point of view wxMaxima is becoming more and more popular in German secondary schools. Is(equal()) is a very helpful command to further Independent learning in Algebra, because pupils could check on their own if some algebraic transformations they made on their own are equivalent or not. From this point of view it would be nescessary that isequal-commands could check polynomial-equations and terms (e.g. with a maximum power of 3?), elementary exponential- and trigonometric equations and terms. But its up to you to decide if didactical aspects should play a role in the decision which commands should be developed or not
Am 08.02.2012 um 12:01 schrieb Stavros Macrakis <macrakis at alum.mit.edu>:
> Could you give some examples of non-trivial situations where this functionality is useful? That might help in thinking about approaches. Your current example is easily handled with 'solve' but of course that won't work when Maxima can't solve the equations.
>
> -s
> On Feb 8, 2012 5:32 AM, "Edd Barrett" <vext01 at gmail.com> wrote:
> On Tue, Feb 07, 2012 at 04:00:23PM -0500, Stavros Macrakis wrote:
> > You could certainly do something like
> >
> > is ( equal( lhs(eq1)-rhs(eq1) , lhs(eq2)-rhs(eq2) ) )
> >
> > as you suggest, but that does NOT test that the truth-values of the
> > equations are the same.
> >
> > After all, 2*x=0 and x=0 are equivalent equations, but 2*x is not equal to
> > x. Logically, what you want is something like
> >
> > is ( equal( zerop(lhs(eq1)-rhs(eq1)) , zerop(
> > lhs(eq2)-rhs(eq2) ) ) )
> >
> > but Maxima doesn't support any such zerop function.
> >
> > You could define zerop(q) := signum(q)^2 , which is perfectly correct, but
> > the <is> system won't be able to do anything useful with that.
> >
> > -s
>
> I am quite suprised that this functionality does not exist. I would have
> thought that equality equivilence would be a commonly used feature in a
> CAS system.
>
> I will raise a feature request and see what the developers say.
>
> Cheers
>
> --
> Best Regards
> Edd Barrett
>
> http://www.theunixzoo.co.uk
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