Re: Re: Problem with Limits; basic calculus
- To: mathgroup at smc.vnet.net
- Subject: [mg39095] Re: [mg39077] Re: Problem with Limits; basic calculus
- From: Garry Helzer <gah at math.umd.edu>
- Date: Wed, 29 Jan 2003 03:36:37 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
In version 4.2.1.1 for Mac OS X both return the same result: the original expression rewritten in two dimensional form On Sunday, January 26, 2003, at 06:44 PM, David W. Cantrell wrote: > "David W. Cantrell" <DWCantrell at sigmaxi.org> wrote: > I just noticed something strange, closely related to the original > question > in this thread, which I can't explain. > > Using version 4.2.0 for Windows: > > Limit[(Exp[-x]-Exp[-2x])/(Exp[-x]+Exp[-2x]), x-> Infinity] > > does not give an answer (although the built-in Limit function _should_ > of course be able to do so) but, merely using an alternative notation, > > Limit[(E^(-x)-E^(-2x))/(E^(-x)+E^(-2x)), x-> Infinity] > > yields, incorrectly, 0 . [The correct answer is 1 .] > > The reason I think of these notations as alternatives is that both > Exp[x] and E^x have FullForm of Power[E, x]. > > So what's going on? Why does the first not give an answer, while the > second gives a wrong answer? > > BTW, using the Standard Add-on Package Calculus`Limit`, _both_ give the > incorrect answer 0 . > > PLEASE do not respond with "workarounds". I know several already, the > easiest of which is to just do the problem in my head! > > David Cantrell > > Garry Helzer Department of Mathematics University of Maryland 1303 Math Bldg College Park, MD 20742-4015