Re: Question: ABS and \[Prime]

*To*: mathgroup at smc.vnet.net*Subject*: [mg47484] Re: Question: ABS and \[Prime]*From*: "David W. Cantrell" <DWCantrell at sigmaxi.org>*Date*: Wed, 14 Apr 2004 07:16:32 -0400 (EDT)*References*: <c5gfrm$apq$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

wellsed at wam.umd.edu (Ed Wells) wrote: > In my notebook output, a copy of which can be seen at : > > www.glue.umd.edu/~wellsed/derivatives.html > > I'm finding the derivatives of a complex function involving distances > (R[] is a distance function) in an energy function (W[] is an energy > function). Having looked at your notebook, I must guess that, when you said "complex" above, you simply meant "complicated". Perhaps Abs was used merely to avoid getting a negative number under Sqrt. If that is the case, then look at the thread "Abs function", started earlier this month by nikmatz, at <http://groups.google.com/groups?threadm=c4j9sq%24dha%241%40smc.vnet.net>. > Each of my derivatives looks okay except for the presence > of the Abs[] function with a \[Prime] following it. It does not > appear in every instance, but I cannot find any documentation for what > this may mean. An example is in the first line of Out[36]. As explained in the cited thread, the prime mark means "derivative". That thread also gives ways to avoid getting Abs', assuming that your quantities are real numbers. HTH, David