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Re: Questions about assumptions

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  • Subject: [mg101797] Re: [mg101749] Questions about assumptions
  • From: "David Park" <djmpark at>
  • Date: Fri, 17 Jul 2009 05:04:48 -0400 (EDT)
  • References: <5024475.1247748242478.JavaMail.root@n11>

I think that $Assumptions is only picked up by expressions that take the
Assumptions option. It does not automatically get spread to everywhere. For
example, Simplify takes the Assumptions so:

$Assumptions = Element[g, Reals];

Conjugate[g] // Simplify

Conjugate[f] // Simplify

David Park
djmpark at  

From: Alexander Erlich [mailto:alexander.erlich at] 


I would like to make assumptions like e.g. Element[a,Reals] or b>0 or
simlar ones global in order to avoid using Refine with long assumption
lists every tome. For this purpose, I've found $Assumptions. But I
encountered the following problem:

In[5]:= $Assumptions = Element[g, Reals]

Out[5]= g \[Element] Reals

In[6]:= Conjugate[g]

Out[6]= Conjugate[g]

Why didn't Mathematica just return g?

Maybe, there is a different, or even better way to make assumptions
global to the whole notebook, so that they are considered
automatically (and without Refine or similar)?



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