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Re: About Reduce and domains

  • 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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