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Re: Grad in VectorAnalysis`

  • To: mathgroup at smc.vnet.net
  • Subject: [mg103840] Re: [mg103822] Grad in VectorAnalysis`
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Fri, 9 Oct 2009 07:14:32 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

Because the definition of f has only two arguments whereas it is called with three in the Grad.

Either call it with two or redefine it with three.


Bob Hanlon

---- Murray Eisenberg <murray at math.umass.edu> wrote: 

=============
After...

   Needs["VectorAnalysis`"]
   SetCoordinates[Cartesian[x, y, z]]

   f[x_, y_] = x/(1 - x^2 - y^2)

... why does the following not actually return the formula for gradient...

   Grad[f[x, y, z]]  (* or even Grad[Evaluate[f[x,y,z]]]

... whereas the following does return it:

   Grad[x/(1 - x^2 - y^2)]



-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305



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