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Re: Limits and Direction

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93846] Re: [mg93818] Limits and Direction
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Thu, 27 Nov 2008 05:28:51 -0500 (EST)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200811261016.FAA19791@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

Actually, the meaning of that option is perfectly reasonable: it means 
that the limit is taken as values of the variable march in the same 
direction as the direction of 1 from the origin, that is, towards 
increasing values.  Thus: limit from the left.

The trouble, of course, is that this mnemonic can be misinterpreted to 
mean that the variable is approaching the fixed value FROM the direction 
that is the direction of 1 from 0, that is, from the right.

"Intuitive" is in the mind of the beholder.

stpatryck 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
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


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