Re: Re: Limit question
- To: mathgroup at smc.vnet.net
- Subject: [mg31528] Re: Re: Limit question
- From: Otto Linsuain <linsuain at andrew.cmu.edu>
- Date: Fri, 9 Nov 2001 06:13:33 -0500 (EST)
- Approved: Steven M. Christensen <steve@smc.vnet.net>, Moderator
- Sender: owner-wri-mathgroup at wolfram.com
Well Erk, there is something wrong with that. It is misleading! If the Limit is not independent of the direction, then, strictly speaking, the Limit does not exist. Mathematica should not give you a value for the Limit in that case unless you specify the Direction. Or it should at least specify under what conditions you get what limit. For example, when you ask Mathematica for an integral that depends on some parameters it might give you a conditional answer, something like If[parameters satisfy some condition, one answer, another answer] With the Limit function, this is complicated because there is a continuum of possible directions on the complex plane. If it was just Direction -> -1 or +1, then I am sure the fellows at Wolfram would have solved this long ago. As for the limits Limit[1/x, x->0] and Limit[Tan[x],x->Pi/2], without specifying a direction, the correct answer is that they don't exist. Otto Linsuain. On Thu, 8 Nov 2001, Erk Jensen wrote: > > Why not? What's wrong with that? > If you don't specify the direction, why should it assume that you want the > limit from the left? > > Why is Limit[1/x,x->0] = infinity? Shouldn't that by your logic be -infinity? > > Your solution obivously is to specify the direction! > > Ciao > -erk- > >