On Sep 23, 1:37 pm, sps <debernasave...@libero.it> wrote:
> And why is it? I do an assignement but it doesn't accept it:
>
> TypeError: Computation failed since Maxima requested additional
> constraints (try the command 'assume((a-1)*(a+1)>0)' before integral
> or limit evaluation, for example):
> Is (a-1)*(a+1) positive, negative, or zero?
> sage: assume((a-1)*(a+1)>0)
> sage: integral(cos(t)/(a+cos(t)),t,0,2*pi)
> ERROR: An unexpected error occurred while tokenizing input
Unfortunately, Maxima's assumption framework (as discussed elsewhere
on the Sage lists currently) is not really that strong, and it turns
out that in this case the error message we give you in Sage won't be
enough to do it. In general, it isn't possible to anticipate all the
possible assumptions one might need, and it's not worth doing it
recursively because of what I just said.
In this case, I ended up having to answer four different questions to
cycle through in Maxima:
sage: var('a t')
(a, t)
sage: assume(a>-1)
sage: assume(a>1)
sage: assume(sqrt(a^2-1)+a-1>0)
sage: assume(abs(sqrt(a^2-1)-a)-1>0)
sage: integral(cos(t)/(a+cos(t)),t,0,2*pi)
2*pi
Notice that the questions change if you make different assumptions:
sage: forget()
sage: assume(a>-1)
sage: assume(a<1)
sage: assume(acos(a)+pi>0)
sage: assume(acos(a)-pi>0)
sage: integral(cos(t)/(a+cos(t)),t,0,2*pi)
ValueError: Integral is divergent.
So sometimes even if you *do* have assumptions working properly, there
are so many paths in the decision tree that it would be very hard to
do this sort of thing. I hope that helps you - I guess to me that is
one thing that makes math interesting!
- kcrisman
--
To post to this group, send email to sage-support@googlegroups.com
To unsubscribe from this group, send email to
sage-support+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sage-support
URL: http://www.sagemath.org
