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MathGroup Archive 2003

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Re: imposing parameter assumptions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg44198] Re: imposing parameter assumptions
  • From: bobhanlon at aol.com (Bob Hanlon)
  • Date: Sun, 26 Oct 2003 00:41:52 -0400 (EDT)
  • References: <bndkco$g6f$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Use Simplify

f[a]=a^-3;

Simplify[#[f[a]], a<0]& /@ 
  {Sign, Positive, Negative, NonNegative}

{-1,False,True,False}


Bob Hanlon

In article <bndkco$g6f$1 at smc.vnet.net>, "drr7" <rondeau at uvic.ca> wrote:

<< Simple question:  How do I impose assumptions on the sign of parameters in
symbolic equations and then test for the sign of an expression. Example:
suppose I want to test the sign of f[a]=a^-3 if a<0.  I tried combinations
of Refine and Positive, but that does not seem to work for me.  What I am
really trying to do is sign a long expression for a derivative.
 >><BR><BR>


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