Re: Abs[x] function
- To: mathgroup at smc.vnet.net
- Subject: [mg87857] Re: Abs[x] function
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Fri, 18 Apr 2008 07:12:39 -0400 (EDT)
- Organization: Uni Leipzig
- References: <fu9fn7$c8d$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
Hi, because you have forgotten to define Derivative[1][Abs][x_] := Sign[x] Regards Jens Vladislav wrote: > Who can explain the behavior. THe derivative Abs[x] at x=.5 is well > defined and is equal to 1. > > In[1]:= D[Abs[x], x] > > Out[1]= > \!\(\*SuperscriptBox["Abs", "\[Prime]", > MultilineFunction->None]\)[x] > > In[2]:= % /. x -> .5 > > Out[2]= > \!\(\*SuperscriptBox["Abs", "\[Prime]", > MultilineFunction->None]\)[0.5] >