Question about to_poly_solve

It looks like to_poly_solve is calling algsys, which is using approximate
methods and thus giving bogus results.

You might try:

         sols: solve( [ trigexpand( sin(x)+cos(x)=cos(2*x) ),
sin(x)^2+cos(x)^2=1 ], [sin(x),cos(x)] )

To get explicit results (rather than sin(x)=...), you can then use %solve:

          map(lambda([eq],%solve(eq,x)), sols);

          -s


On Thu, Jun 13, 2013 at 9:31 AM, Karl-Dieter Crisman <kcrisman at gmail.com>wrote:

> Just putting this one out there.  Is there some obvious simplification I'm
> missing?
>
> (%i2) load(to_poly_solve);
>
> Loading maxima-grobner $Revision: 1.6 $ $Date: 2009-06-02 07:49:49 $
> (%o2)
> /Users/karl.crisman/Downloads/sage-5.9.rc1/local/share/maxima/5.29.1/sha\
> re/to_poly_solve/to_poly_solve.mac
> (%i3) to_poly_solve(sin(x)+cos(x)=cos(2*x),x);
> (%o3) %union([x =
>   - 254453378946433024 %pi %z10 - 113 %i + 199847233464565760
> - -----------------------------------------------------------],
>                       127226689473216512
>        - 5428338750857237544 %pi %z12 - 452 %i + 2131703823622034655
> [x = - -------------------------------------------------------------],
>                             2714169375428618772
>        - 2035627031571464192 %pi %z14 - 113 %i - 2398166801574789120
> [x = - -------------------------------------------------------------],
>                             1017813515785732096
> [x = 2 %pi %z8])
> (%i4) solve(sin(x)+cos(x)=cos(2*x),x);
> (%o4)                    [cos(2 x) = sin(x) + cos(x)]
>
>
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