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Re: Simplify problems for checking easy equalities...
*To*: mathgroup at smc.vnet.net
*Subject*: [mg53860] Re: Simplify problems for checking easy equalities...
*From*: "Drago Ganic" <drago.ganic at in2.hr>
*Date*: Tue, 1 Feb 2005 04:08:10 -0500 (EST)
*References*: <cti5nd$8n2$1@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
Hi Cyrus,
use assumptions! The simplification qou expect is not generally valid.
Simplify or Refine are enough for the elementary functions!
FullSimplify[Log[x^n] - n Log[x], n \[Element] Integers && x > 0]
0
Simplify[Log[x^n] - n*Log[x], n \[Element] Integers && x > 0]
0
Refine[Log[x^n] - n*Log[x], n \[Element] Integers && x > 0]
0
Those assumptions are used implicity in the unary function PowerExpand:
Log[x^n] - n*Log[x] // PowerExpand
0
Greetings,
Drago
"Cyrus Erik Eierud" <cyruserik at tele2.se> wrote in message
news:cti5nd$8n2$1 at smc.vnet.net...
> 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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