Re: [Maxima-discuss] probable bug in sqrt

[Michel T. <ta...@lp...>]

Le 09/11/2025 à 17:42, Igor Pesando a écrit :
> Hi*,
>
> I have a linear system of 5 eqs in 7 unknows cA[1]... cA[7]
>
> The system depends also on a parameter d.
>
> I solve the system for 5 unknowns cA[1] .. cA[5].
>
> So the solution depends on cA[6], cA[7] and d.
>
> I substitute back and I do not find zero, one of the reason I cannot 
> convince maxima to simplify expressions containing sqrt(7 - 4 *sqrt(3)).
>
> So I substitute some values of d and I still do not get zero.
>
> Since I know the solution of the system for d=26 and I noticed that 
> substituting d=26 before solving or after solving yields some sign 
> differences
>
> I guess the issue is in sqrt. By the w

By the way, if one fixes explicit values for d, and one adds a ratsimp 
at the end, the program works ok. For example

(%i1) domain:complex$

(%i2) d:1234;
(%o2)                                1234
(%i3) eqsAT: [
....................................
]$

(%i4) unksAT:[cA[5],cA[4],cA[3],cA[2],cA[1]]$

(%i5) soAT:linsolve(eqsAT, unksAT)$

(%i6) zeAT:ratsimp(subst(soAT, eqsAT));
(%o6)                           [0, 0, 0, 0, 0]
(%i7)

I have tried with many values of d it always work OK.


-- 

Michel Talon