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MathGroup Archive 2000

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Re: How do I force Log[Exp[x]]=x

  • To: mathgroup at smc.vnet.net
  • Subject: [mg22025] Re: [mg21988] How do I force Log[Exp[x]]=x
  • From: Andrzej Kozlowski <andrzej at platon.c.u-tokyo.ac.jp>
  • Date: Fri, 11 Feb 2000 02:38:08 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

In Mathematica 4

In[3]:=
Simplify[Log[Exp[x]], Element[x, Reals]]

Out[3]=
x

In earlier versions:

In[4]:=
PowerExpand[Log[Exp[x]]]

Out[4]=
x

> From: sasrbk at unx.sas.com (Bart Killam)
To: mathgroup at smc.vnet.net
> Organization: SAS Institute
> Date: Thu, 10 Feb 2000 02:25:32 -0500 (EST)
> To: mathgroup at smc.vnet.net
> Subject: [mg22025] [mg21988] How do I force Log[Exp[x]]=x
> 
> 
> For real x, Log[Exp[x]]=x. For general complex x
> Mathematical leaves this expression unevaluated. I
> have tried Log[Exp[x/;Im[x]=0]], but this give a result
> of 0. 
> 
> How do I tell Mathematica that I want the expression
> simplied for real x ? Thanks for any help.
> -- 
> Bart Killam                            Work:  919-677-8000 x7538
> SAS Institute Inc.                     Fax:   919-677-8123
> SAS Campus Dr., R5115                  Email: sasrbk at unx.sas.com
> Cary NC 27513-8000
> 



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