Re: Grad in VectorAnalysis`

*To*: mathgroup at smc.vnet.net*Subject*: [mg103868] Re: Grad in VectorAnalysis`*From*: Albert Retey <awnl at gmx-topmail.de>*Date*: Fri, 9 Oct 2009 07:20:00 -0400 (EDT)*References*: <hakjlm$d72$1@smc.vnet.net>

Murray Eisenberg 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]]] I think this is just a typo, Grad[f[x,y]] works as expected, using Grad[f[x,y,z]] doesn't work since you only defined f[x_,y_]... > ... whereas the following does return it: > > Grad[x/(1 - x^2 - y^2)] > > >