• To: mathgroup at smc.vnet.net
• Subject: [mg98662] Re: About Reduce and domains
• From: dh <dh at metrohm.com>
• Date: Thu, 16 Apr 2009 04:10:39 -0400 (EDT)
• References: <grupt9\$s5\$1@smc.vnet.net>

```
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.

>

```

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