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Limit question

  • To: mathgroup at
  • Subject: [mg73072] Limit question
  • From: "dimitris" <dimmechan at>
  • Date: Thu, 1 Feb 2007 03:19:00 -0500 (EST)

Practising with the Limit command I discover the following setting

(Limit[Log[z], z -> -1, Direction -> #1] & ) /@ {I, -I}

{(-I)*Pi, I*Pi}

So my simple question is if it is somewhere documented in the
Mathematica Book that you can use other values than just {1,-1} for
the Direction Option. Note that


>From In[481]:=
"Direction is an option for Limit. Limit[expr, x -> x0, Direction ->
1] computes the limit as x approaches x0 from smaller \
values. Limit[expr, x -> x0, Direction -> -1] computes the limit as x
approaches x0 from larger values. Direction -> Automatic \
uses Direction -> -1 except for limits at Infinity, where it is
equivalent to Direction -> 1."

>From In[481]:=
Attributes[Direction] = {Protected}

Note also that even in this link
in which for some Built-In functions you can find additional
information (for example
Integrate.html )
there is no other information.


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