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Re: Limits and Direction

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93830] Re: Limits and Direction
  • From: dimitris <dimmechan at yahoo.com>
  • Date: Wed, 26 Nov 2008 07:22:21 -0500 (EST)
  • References: <ggj7l1$jad$1@smc.vnet.net>

On 26 =CD=EF=DD, 12:16, stpatryck <stpatr... at gmail.com> wrote:
> Fellow Mathematica Users:
>
> Why is it that when using the Limit[ ] function, Direction -> 1
> indicates a left hand limit?  This really seems counterintuitive.
>
> Is there a way to switch it?
>
> Thanks,
> Patrick

It's a matter of convention.
For example

In[11]:=
f[x_] := 1/x

In[17]:=
Plot[f[x], {x, -1, 1}]

In[12]:=
Limit[f[x], x -> 0]
Limit[f[x], x -> 0, Direction -> 1]
Limit[f[x], x -> 0, Direction -> -1]

Out[12]=
Infinity

Out[13]=
-Infinity

Out[14]=
Infinity

I think it's not a good idea to change built-in functions like Limit.
Instead you should
define your own limit function.

Dimitris


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