On 06/24/2012 11:07 AM, Barton Willis wrote:
>> For the more general problem, below, solve() actually executes for a
>> very long time before coming back with a null solution, using your
>> current definition of ebaksubst :
> The algorithm used by algys just isn't up to this task; the only workaround I know is to use the grobner package.
> The optional package to_poly_solve provides a convenient way to call grobner:
>
> (%i21) sol : to_poly_solve([(x-a)^2 + (y-b)^2 = r1^2,(x-c)^2 + (y-d)^2 = r2^2], [x,y], 'use_grobner = true)$
>
> Specialize:
>
> (%i22) subst([a=0,b=0, c=1/2,d=1/2,r1=1,r2=1], sol);
> (%o22) %union([x=1/4-sqrt(7)/4,y=sqrt(7)/4+1/4],[x=sqrt(7)/4+1/4,y=1/4-sqrt(7)/4])
>
> Specialize--oops, not OK for all values of the parameters:
>
> (%i23) subst([a=0,b=0, c=0,d=0,r1=1,r2=1], sol);
> expt: undefined: 0 to a negative exponent.
>
> For to_poly_solve to autoload like this, you'll need Maxima 2.27, I think
>
>
>
>
Perhaps solve(), or algsys() can be made to recognize that the problem
requires a call to_poly_solve() and compute accordingly.
By the way, did you mean Maxima 5.27? The poly solver package in Maxima
5.24 seems to be buggy, since it also fails to solve the original
problem (with 'use_grobner=true).
Krishna