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Re: Grad in VectorAnalysis`

• To: mathgroup at smc.vnet.net
• Subject: [mg103862] Re: [mg103822] Grad in VectorAnalysis`
• From: "David Annetts" <david.annetts at iinet.net.au>
• Date: Fri, 9 Oct 2009 07:18:51 -0400 (EDT)
• References: <200910081149.HAA13507@smc.vnet.net>

Hi Murray,

> 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)]

At a guess, it's because of how you've defined f ....

D.

• References:
  • Grad in VectorAnalysis`
    • From: Murray Eisenberg <murray@math.umass.edu>