Re: positive numbers
- To: mathgroup at smc.vnet.net
- Subject: [mg17539] Re: positive numbers
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Fri, 14 May 1999 01:13:10 -0400
- Organization: Universitaet Leipzig
- References: <7h4hrp$ed4@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi Ulf,
in general you can't.
You can use the Assumptions-option of Integrate[] to get
Integrate[Exp[-a*x^2],{x,-Infinity,Infinity},Assumptions->{a>0}]
and you can setup definitions like
a /: Positive[a]:=True
but this will probably only work for your own transformations.
Hope that helps
Jens
Ulf Saalmann wrote:
>
> Hej,
>
> a simple question: How can I inform Mathematica
> that a variable is always positive without giving
> a specific value (in order to avoid distinction of
> cases).
>
> Thanks Ulf. (us at atom.msi.se)