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Re: Limit and Abs

  • To: mathgroup at
  • Subject: [mg31219] Re: [mg31194] Limit and Abs
  • From: Tomas Garza <tgarza01 at>
  • Date: Fri, 19 Oct 2001 03:12:12 -0400 (EDT)
  • References: <>
  • Sender: owner-wri-mathgroup at

And what, may I ask, is the "correct answer"? Your function is periodic with
period Pi. The only answer is

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

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

And, unless there is a misprint in your second expression below, the limit
with *n* -> Infinity has to remain unevaluated, because a is not defined.
But, then, if there is a misprint and you meant a -> Infinity instead of
n->Infinity, the function is again periodic with period Pi (look at the
graphs). The limit doesn't exist, and Mathematica has no alternative but to
leave the expression unevaluated.

Tomas Garza
Mexico City
----- Original Message -----
From: "Oliver Friedrich" <oliver.friedrich at>
To: mathgroup at
Subject: [mg31219] [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
> unknown ??) so I'm not too surprised or disappointed.
> But anyway, how can I workaround or bypass this problem, maybe an option
> another function in the extra packages ?
> Thanks
> Oliver Friedrich

  • References:
    • Limit and Abs
      • From: "Oliver Friedrich" <>
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