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Re: how to test if 2 expressions are the same? Mathematica 5.0

• To: mathgroup at smc.vnet.net
• Subject: [mg46111] Re: how to test if 2 expressions are the same? Mathematica 5.0
• From: astanoff at yahoo.fr (Valeri Astanoff)
• Date: Fri, 6 Feb 2004 04:15:39 -0500 (EST)
• References: <bvt135$oj5$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

nma124 at hotmail.com (steve_H) wrote in message news:<bvt135$oj5$1 at smc.vnet.net>...
> hello;
> 
> I am confused.
> 
> many times, I want to find if there is a way to obtain one expression
> from another by tranformation.
> 
> for example, we know that 1-sin^2(x) = cos^2(x), and  a*log(x)=log(x^a),
> etc.., but sometimes this does not seem to work using SameQ:
> 
> SameQ[a Log[x], Log[x^a] ]
> False
> 
> I tried MatchQ and that also gives False.
> 
> what is the right way to do these things in Mathematica? I checked the on-line help,
> and can't seem to see the right command for this.
> 
> many thanks,
> STeve
I think you have to tell Mathematica that 'a' and 'x' are positive :
In[1]:=a Log[x]- Log[x^a] // Simplify[#, x>0 && a>0]&
Out[1]=0
but it doesn't seem to work with SameQ!