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Assume and $Assumptions and Results

  • To: mathgroup at smc.vnet.net
  • Subject: [mg102216] Assume and $Assumptions and Results
  • From: ivo welch <ivowel at gmail.com>
  • Date: Sat, 1 Aug 2009 04:02:49 -0400 (EDT)

[Easy Beginner's Query]


Dear Experts:

My goal is to input a set of assumptions for various variables, and then
determine whether an expression of these variables (a long derivative that
is a few lines) is true or false. That is, I want to input many conditions,
such as "$Assumptions = (x>y) && (y>1)" and then ask Mathematica whether "1/(X+Y) >
1.5" is true, for example.

Alas, I am a little stuck on home plate:
   Simplify[ x > 1, x>0 ]
given that x is greater than 0, isn't it supposed to be True?  Instead Mathematica 
returns "x>1".  It also does not help to make the condition "(x
<esc>elem<esc> Reals) && (x>0)" .


(Another brief questions:  do $Assumptions assignments add or replace
earlier assumptions?)


Help appreciated.  Am I expecting too much of Mathematica?

/iaw



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