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MathGroup Archive 2004

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Re: can't MATHEMATICA simplify simple expressions?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51540] Re: can't MATHEMATICA simplify simple expressions?
  • From: adam.smith at hillsdale.edu (Adam Smith)
  • Date: Thu, 21 Oct 2004 22:21:09 -0400 (EDT)
  • References: <cl4tg0$8g7$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

The problem is that you are assuming that "a" is a real number.  While
this is normal for most humans, it need not be in a strict
mathematical sense.  By default Mathematica assumes all variables can
be complex.  For a complex number the result is not simply a^3.

You can place conditions on the simplicication:
For example if a>0

 In[4]:=
FullSimplify [ (a^2)^(3/2),a>0 ] 

Out[4]=
a^3

For a simply a real number

In[5]:=
FullSimplify [ (a^2)^(3/2),Element[a,Reals] ] 

Out[5]=
Abs[a]^3

Cole Turner <REMOVEcole.tuner at liwest.at> wrote in message news:<cl4tg0$8g7$1 at smc.vnet.net>...
> if I enter:
> 
> FullSimplify [ (a^2)^(3/2) ]
> 
> (in correct MATHEMATICA syntax, the program does not yield the correct
> result, a^3 ... 
> 
> why is that?
> 
> thanks!


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