On Mon, Nov 3, 2008 at 9:04 AM, Martin Rubey wrote: > > Francois Maltey writes: > >> Alejandro Jakubi wrote: >> > I wonder how it is done in Axiom the selection of roots of a >> > polynomial with some property. As in this example, select the >> > positive roots out of the list of three roots generated by: >> > >> > radicalSolve(p^3-p+1/10=0,p) >> >> With fricas I get a mysterious result and a fuzzy bug. >> >> First I get 3 radical roots, >> second I get [p=3/20] >> and third I get [p=(10pl3+1)/10]. > > You are saying you get different results for the same input? This doesn't > seem to happen here - I always get the same 3 radical roots, and actually,
I also can not understand what Francois is saying. > the whole thing works as nicely as it could here: (FriCAS, svn revision > around 430) > > (1) -> LR := radicalSolve (p^3-p+1/10=0,p) > > (1) > +------------------+2 > | +-+ +-----+ > +---+ |- 3\|3 + \|- 373 > (- 3\|- 3 + 3) |------------------ - 2 > 3| +-+ > \| 60\|3 > [p= -----------------------------------------, > +------------------+ > | +-+ +-----+ > +---+ |- 3\|3 + \|- 373 > (3\|- 3 + 3) |------------------ > 3| +-+ > \| 60\|3 > +------------------+2 > | +-+ +-----+ > +---+ |- 3\|3 + \|- 373 > (- 3\|- 3 - 3) |------------------ + 2 > 3| +-+ > \| 60\|3 > p= -----------------------------------------, > +------------------+ > | +-+ +-----+ > +---+ |- 3\|3 + \|- 373 > (3\|- 3 - 3) |------------------ > 3| +-+ > \| 60\|3 > +------------------+2 > | +-+ +-----+ > |- 3\|3 + \|- 373 > 3 |------------------ + 1 > 3| +-+ > \| 60\|3 > p= ---------------------------] > +------------------+ > | +-+ +-----+ > |- 3\|3 + \|- 373 > 3 |------------------ > 3| +-+ > \| 60\|3 > Type: List(Equation(Expression(Integer))) > Well, because the discriminant is positive there are three *real* roots but Axiom apparently cannot simplify these expressions to make it obvious. As a result, Axiom cannot select the positive ones. So maybe it is not as nice as it could be. Regards, Bill Page. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/fricas-devel?hl=en -~----------~----~----~----~------~----~------~--~---
