• To: mathgroup at smc.vnet.net
• Subject: [mg98798] Re: About Reduce and domains
• From: olfa <olfa.mraihi at yahoo.fr>
• Date: Mon, 20 Apr 2009 01:27:22 -0400 (EDT)
• References: <grupt9\$s5\$1@smc.vnet.net> <gs6p5p\$gmb\$1@smc.vnet.net>

```On 16 avr, 10:10, dh <d... at metrohm.com> wrote:
> Hi,
>
> if you want something like x>0... then you specify a domain implicitly.
>
>   For a complex number x>0 does not make much sense.
>
> Note that you may also specify the domain of some variables in the first
>
> argument of Reduce:
>
> Reduce[{..,Element[{x,y},Reals],..}]
>
> Daniel
>
>
>
> olfa wrote:
> > Hi Mathematica community,
>
> > I remarqued in many outputs with reduce, that mathematica treats some
> > parameters as complexe numbers and consequently distinguich between Re
> > part and Im part:
> >  For example:
> > (Re[d]<0&&Re[a]<0&& ...) || (Re[d]<0&&Re[a]==0&&Im[a]<0&& ...) || (=
Re
> > [d]<0&&Re[a]==0&&Im[a]>0&&...) || (Re[d]<0&&Re[a]>0&&...) || (Re[d]
> > ==0&&Im[d]<0&&Re[a]<0&&...) ||...
>
> > In the help I have read that Reduce[expr,vars] assumes by default that
> > quantities appearing algebraically in inequalities are real, while all
> > other quantities are complex.
>
> > But is there a mean to force mathematica in the way that it does not
> > distinguich between real part and imaginary part in the output and
> > consequently to have: d<0 && a<0 ...|| d==0 && a>0 || ...without
> > specifying a domain which means without Reduce[expr,vars,doms]?
>
> > Thank you very much.- Masquer le texte des messages pr=E9c=E9dents -
>
> - Afficher le texte des messages pr=E9c=E9dents -

Hi daniel,
the problem is that I dont know in advance which variables should I
put in Element because it depends on which variables mathematica treat
as complexe in the output. so how to deal with that?

```

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