Re: Question about the derivative of Abs
- To: mathgroup at smc.vnet.net
- Subject: [mg106116] Re: Question about the derivative of Abs
- From: dh <dh at metrohm.com>
- Date: Sat, 2 Jan 2010 05:03:19 -0500 (EST)
- References: <hhkj64$53d$1@smc.vnet.net>
Hi Sam, mathematica does not know the derivative of Abs, but it is easy to add a corresponding rule: Abs'[x_?Positive] = 1 Abs''[x_?Positive] = 0 Daniel On 1 Jan., 11:35, Sam Takoy <samta... at yahoo.com> wrote: > Hi, > > I kind of asked this question before, but in a more confusing context, > so now I would like to ask it by itself. > > In the course of my computations, I get Abs' and Abs''. It is applied to > a positive number, so I think those values should be 1 and 0. However, > Mathematica fails to simplify it. > > For example > > In[34]:= Abs'[2.0] > > Out[34]= > \!\(\*SuperscriptBox["Abs", "\[Prime]", > MultilineFunction->None]\)[2.] > > These expressions really mess up my answers. How do I get Mathematica to > do these simplifications? > > Thanks > > Sam