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MathGroup Archive 2005

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Re: Simplify problems for checking easy equalities...

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53876] Re: [mg53856] Simplify problems for checking easy equalities...
  • From: yehuda ben-shimol <benshimo at bgumail.bgu.ac.il>
  • Date: Tue, 1 Feb 2005 04:08:28 -0500 (EST)
  • References: <200501300818.DAA08843@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

You only need to add some assumptions to your expressions, since for some set 
of values the Log[] is not defined 
For example use 
FullSimplify[Log[x^n] - n*Log[x], Assumptions -> x > 0 && n > 0]
and it will return 0 as expected
yehuda

On Sunday 30 January 2005 10:18, Cyrus Erik Eierud wrote:
> Please Help!
>
> Thanks for all great answers I've already found here!
> My problem is that I can not simplify what to me seems as a very
> simple equality task. This is what I want Mathematica to return zero
> for:
>
> in[1]:= FullSimplify[Log[x^n] - n*Log[x]]
>
> out[1]= -n Log[x] + Log[x^n])
>
> I have used Simplify to check equalities, but the one above (and many
> other equations similar to the one above) just don't simplify. Am I
> doing anything wrong or does anyone know of a better way to check
> equalities?
>
> Appreciate any help,
> Cyrus Eierud, Student
> cyruserik at tele2.se


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