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Re: Re: Grad in VectorAnalysis`

  • To: mathgroup at smc.vnet.net
  • Subject: [mg103889] Re: [mg103840] Re: [mg103822] Grad in VectorAnalysis`
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Sat, 10 Oct 2009 07:11:36 -0400 (EDT)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200910091114.HAA25788@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

D'oh!

Thanks to all who responded.

Bob Hanlon wrote:
> 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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