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Re: Assume and $Assumptions and Results
*To*: mathgroup at smc.vnet.net
*Subject*: [mg102247] Re: [mg102216] Assume and $Assumptions and Results
*From*: Murray Eisenberg <murray at math.umass.edu>
*Date*: Sun, 2 Aug 2009 06:02:12 -0400 (EDT)
*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst
*References*: <200908010802.EAA07200@smc.vnet.net>
*Reply-to*: murray at math.umass.edu
Unless x already has a specific numeric value, the correct result of
Simplify[x > 1, x > 0]
is:
x > 1
This result is the same as that of:
Simplify[x > 1 && x > 0]
It would be redundant to include Element[x,Reals], since x > 0 already
implies that.
ivo welch wrote:
> [Easy Beginner's Query]
>
>
> Dear Experts:
>
> My goal is to input a set of assumptions for various variables, and then
> determine whether an expression of these variables (a long derivative that
> is a few lines) is true or false. That is, I want to input many conditions,
> such as "$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
>
>
--
Murray Eisenberg murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower phone 413 549-1020 (H)
University of Massachusetts 413 545-2859 (W)
710 North Pleasant Street fax 413 545-1801
Amherst, MA 01003-9305
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