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MathGroup Archive 2002

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Re: FullSimplify[Abs[Sign[x]],x>=0] equals 1?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg33730] Re: [mg33691] FullSimplify[Abs[Sign[x]],x>=0] equals 1?
  • From: BobHanlon at aol.com
  • Date: Wed, 10 Apr 2002 00:49:13 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 4/9/02 1:29:40 AM, al2 at noos.fr writes:

>Is the following behavior normal?  
>
>
>In[1]:= Simplify[Abs[Sign[x]],x>=0]
>
>Out[1]= Abs[Sign[x]]
>
>In[2]:= FullSimplify[Abs[Sign[x]],x>=0]
>
>Out[2]= 1
>
>In[3]:= $Version
>
>Out[3]= 4.1 for Sun Solaris (November 8, 2000)
>
>
>In this case I would have expected FullSimplify to give the save
>answer as Simplify, as I was (naively?) assuming Abs[Sign[0]] equals
>zero.  What am I missing?  (Note I get the same output 
>for Version 4.0 for Linux (July 22, 1999).)
>

I have the same problem on a Mac with OS X

$Version

4.1 for Mac OS X (November 5, 2001)

Simplify[Abs[Sign[x]],x>=0]

Abs[Sign[x]]

FullSimplify[Abs[Sign[x]],x>=0]

1


Bob Hanlon
Chantilly, VA  USA


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