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MathGroup Archive 2001

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RE: Limit and Abs

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31212] RE: [mg31194] Limit and Abs
  • From: Bradley Stoll <BradleyS at Harker.org>
  • Date: Fri, 19 Oct 2001 03:12:02 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

That's interesting.  When I evaluate Limit[Abs[Cot[a]]/(Abs[Cot[a]] + 2), a
-> Infinity], Mathematica returns 1, which does not make sense when you view the
graph.  When I evaluate Limit[Cot[a]/(Cot[a] + 2), a -> Infinity], Mathematica
returns Abs[Cot[a]]/(2 + Abs[Cot[a]]).  Can someone explain this?  By the
looks of it, neither of these limits exist, which is what I would've thought
in the first place.  I'm using 4.1, by the way.

Bradley Stoll

-----Original Message-----
From: Oliver Friedrich [mailto:oliver.friedrich at tz-mikroelektronik.de]
To: mathgroup at smc.vnet.net
Subject: [mg31212] [mg31194] Limit and Abs


Hallo,

if I evaluate
Limit[Cot[a]/(Cot[a]+2),a->Infinity]
i get the correct answer.

But I want to evaluate

Limit[Abs[Cot[a]]/(Abs[Cot[a]]+2),n->Infinity]

and that's being returned unevaluated. Help states, that Limit will return
expressions unevaluated, if there are functions with unknown behaviour (Abs
unknown ??) so I'm not too surprised or disappointed.
But anyway, how can I workaround or bypass this problem, maybe an option or
another function in the extra packages ?

Thanks

Oliver Friedrich



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