Re: Re[a]>0 ?
- To: mathgroup at smc.vnet.net
- Subject: [mg6241] Re: [mg6198] Re[a]>0 ?
- From: Mats Jirstrand <matsj at isy.liu.se>
- Date: Fri, 28 Feb 1997 03:22:27 -0500
- Organization: Linköping University, Sweden
- Sender: owner-wri-mathgroup at wolfram.com
Jens Dreger wrote: > > Hi ! > > Can anyone tell me how I can make MMA take Re[a] for greater than 0 ? > > In[1]:= Integrate[E^(-a*x^2), {x, -Infinity, Infinity}] > > Out[1]:= If[Re[a] > 0, Sqrt[Pi]/Sqrt[a], > Integrate[E^(-a*x^2), {x, -Infinity, Infinity}]] > > I would like to have just the answer "Sqrt[Pi]/Sqrt[a]", since I know > that Re[a]>0 is true. > > BTW: a/:Re[a]=1 works, but I don't want to specify the real part of a, > just want to say it's greater than zero. > > Thanks ! > > Jens. Jens, use the Assumptions option for Integrate! In[1]:= Integrate[E^(-a*x^2),{x, -Infinity, Infinity},Assumptions->Re[a]>0] Out[1]= Sqrt[Pi]/Sqrt[a] ~~~Mats ________________________________________________________ Mats Jirstrand | Division of Automatic Control /|\ Dept. of EE, Linkoping University \|/ S-581 83 Linkoping, Sweden /|\ Tel: +46 13 284042 / | \ Fax: +46 13 282622 () | () Email: matsj at isy.liu.se WWW: http://www.control.isy.liu.se