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Re: querries

  • To: mathgroup at smc.vnet.net
  • Subject: [mg119566] Re: querries
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Fri, 10 Jun 2011 06:38:48 -0400 (EDT)

On 6/9/11 at 5:45 AM, savits at pitt.edu (Savits, Thomas H) wrote:

>1)       Why does Mathematica not give the value 0 to the expression
>(mu*lambda)^(b) - (mu^b)*(lambda^b)? It seems to treat the
>expression (mu*lambda) as a new variable. I used the greek letters
>from the palette in the actual expression.

By default, Mathematica assumes variables are complex. If you
assign appropriate complex values to your expression it does not
reduce to 0. You can either tell Mathematica to treat the
variables as real or use PowerExpand which assumes variables are
real. For example,

In[3]:= (mu*lambda)^(b) - (mu^b)*(lambda^b) // PowerExpand

Out[3]= 0

>2)       Many times I cannot get Mathematica to simplify expressions
>involving the exponential functions, e.g., it won't combine the
>arguments of the Exp functions. Is there a way to force this?

Use PowerExpand. Just be aware that the transformations
PowerExpand does are not valid for arbitrary complex values.



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