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Re: Re: Limit Question

• To: mathgroup at smc.vnet.net
• Subject: [mg66479] Re: [mg66459] Re: [mg66452] Limit Question
• From: "David Park" <djmp at earthlink.net>
• Date: Mon, 15 May 2006 23:49:08 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

And yes, the Mathematica Help for Limit DOES now say that Assumptions is an
option - but it is interesting that almost everyone missed that and use the
Assuming statement instead. And wondered why it worked!

I guess it pays to read the Help carefully for newer features, such Assuming
and $Assumptions.

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/

From: Carl K. Woll [mailto:carlw at wolfram.com]
To: mathgroup at smc.vnet.net


Blimbaum, Jerry CIV NSWC PC wrote:
> Why do these give no output?
>
> Simplify[Limit[Exp[-a t],t->Infinity],a>0]
>
> and  same for
>
> Simplify[Limit[Exp[a t],t->Infinity],a<0]
>
> thanks...
>
> Jerry Blimbaum
>
>

Try sticking the assumption inside of Limit:

In[11]:= Limit[Exp[-a t], t -> Infinity, Assumptions -> a > 0]

Out[11]= 0

In[12]:= Limit[Exp[a t], t -> Infinity, Assumptions -> a < 0]

Out[12]= 0

Carl Woll
Wolfram Research