Re: Why doesn't Log[ E^x ] = x ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg24434] Re: Why doesn't Log[ E^x ] = x ?*From*: Paul Abbott <paul at physics.uwa.edu.au>*Date*: Tue, 18 Jul 2000 00:58:32 -0400 (EDT)*Organization*: University of Western Australia*References*: <8jrdc2$e2t@smc.vnet.net> <8k0tnp$q40@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

In article <8k0tnp$q40 at smc.vnet.net>, "Bill Bertram" <wkb at ansto.gov.au> wrote: > Christopher R. Carlen <crcarle at sandia.gov> wrote in message > news:8jrdc2$e2t at smc.vnet.net... > > Hi: > > > > E^Log[x] evaluates to x > > > > but > > > > Log[ E^x ] evaluates to Log[ E^x ] > > > > Why? > > > > > Same for Mathematica Version 4, except if you use "PowerExpand". > > PowerExpand[Log[Exp[x]]] -> x A better (safer) solution is to use Simplify[Log[E^x], Element[x, Reals]] Cheers, Paul -- Paul Abbott Phone: +61-8-9380-2734 Department of Physics Fax: +61-8-9380-1014 The University of Western Australia Nedlands WA 6907 AUSTRALIA http://physics.uwa.edu.au/~paul