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Re: Limit[ArcTan]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg20783] Re: Limit[ArcTan]
  • From: "Bill Bertram" <wkb at ansto.gov.au>
  • Date: Thu, 11 Nov 1999 00:22:53 -0500
  • Organization: Australian Nuclear Science and Technology Organisation
  • References: <80auib$j32@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Alberto Verga wrote in message <80auib$j32 at smc.vnet.net>...
>Why I do not obtain the correct result?
>   ArcTan[x,x^2]/.x->-0.00001
>gives
>   3.14158
>But,
>   Limit[ArcTan[x,x^2],x->0,Direction->-1]
>gives
>   0


Alberto,

You probably misuderstand what is meant by Direction->-1. It means
approaching the limit from the large values to the small value. Thus in your
example  Limit[ArcTan[x,x^2],x->0,Direction->-1]  takes the limit from
positive x to zero. To get the limit you want you need to use Direction ->
+1.

Cheers

   Bill





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