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Re: number types

• To: mathgroup at smc.vnet.net
• Subject: [mg21645] Re: number types
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Fri, 21 Jan 2000 03:59:55 -0500 (EST)
• Organization: Universitaet Leipzig
• References: <861529$jjr@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Hi,

look what the Assumptions-option

?Assumptions

"Assumptions is an option for Integrate and other functions that
specifies \
what assumptions be made about relations between parameters."

and in Mathematica 4.0 FullSimplify[expr,Element[a,Reals]]
can do for you.

Hope that helps

  Jens 

Naum Phleger wrote:
> 
>     I feel sort of silly asking something that should be so clear but after
> LOTS of trying I can't seem to get it right.
> 
> How can I make Mathematica know that a variable is real or positive so that
> 
> Conjugate[a] gives a
> 
> Sqrt[ a^2 ] gives a
> 
> when I evaluate integrals with a in them it doesn't give me an If statement
> like
> 
> If[ Im[a]=0, answer I want   , unevaluated integral ]
> 
>     this seems like it should be easy but I nothing that I try ever works.
> 
> Thanks for any help.