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Re: Problem with Simplify and Assumptions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg119230] Re: Problem with Simplify and Assumptions
  • From: ADL <alberto.dilullo at tiscali.it>
  • Date: Wed, 25 May 2011 19:32:23 -0400 (EDT)
  • References: <irijr5$qfu$1@smc.vnet.net>

On 25 Mag, 11:57, Cisco Lane <travl... at yahoo.com> wrote:
> I am wondering how to get the last line to say "True"
>
> In[1]:= $Assumptions = {m >= 1, s > 0}
>
> Out[1]= {m >= 1, s > 0}
>
> In[3]:= Simplify[(1 - 2*m)*s < 0]
>
> Out[3]= True
>
> In[4]:= Simplify[Exp[(1 - 2*m)*s] < 1]
>
> Out[4]= E^s < E^(2 m s)
>
> Thanks,
> Frank L.

To look around Andrzej Kozlowski's suggestions, I observe that Reduce
seems to be insensitive to $Assumptions or Assuming, which is strange
(to me) and not mentioned in the help.

In any case,

In[]:= Reduce[m>=1 && s>0 && Exp[(1-2*m)*s]<1]
Out[]= m>=1 && s>0

which is a rather unusual way to express that the condition on Exp is
redundant (and thus disappeared).

In fact:

In[]:= Reduce[m >= 1 && s > 0 && Exp[(1 - 2*m)*s] >= 1]
Out[]= False

So, it seems to be easier to get a False than to get a True.

ADL


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