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Re: Is this normal for Limit?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82298] Re: Is this normal for Limit?
  • From: Peter Breitfeld <phbrf at t-online.de>
  • Date: Wed, 17 Oct 2007 04:00:08 -0400 (EDT)
  • References: <ff1par$8nq$1@smc.vnet.net>

Michael Mandelberg schrieb:
> I have what I would think is the following simple limit to evaluate:
>
> $Pre = Refine[#] &;
> $Assumptions = {t \[Element] Reals, k \[Element] Reals,  k > 0};
>
> In[3]:= Limit[Exp[-k t], t -> Infinity]
>
> The results is:
>
> Out[3]= Limit[\[ExponentialE]^(-k t), t -> \[Infinity]]
>
> In other words Mathematica 6.0.0 punts on this.  Is there any sense in
> which this limit is not well-defined?
>
> Michael Mandelberg
>
>
IIRC this was discussed some time ago. $Assumptions now wants a
logical expression instead of a list:

$Assumptions=t \[Element] Reals && k \[Element] Reals &&  k > 0

With this setting you get the limit 0 as expected.

Gruss Peter
-- 
==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de


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