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

**References**:**Re: Grad in VectorAnalysis`***From:*Bob Hanlon <hanlonr@cox.net>