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

**Follow-Ups**:**Re: Re: Grad in VectorAnalysis`***From:*Murray Eisenberg <murray@math.umass.edu>