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Robert Astalos
01/20/97 6:25pm

Reply to message #101 from Lars Holmstrom: > Following an example
straight out of a > Mathematica supplement for an Engineering > Mathematics
book, I get the wrong output > than I should: > > In[1]:= <<Calculus`VectorAnalysis`
> > In[2]:= F = {7 x, 0, -z} > > Out[2]= {7 x, 0, -z} > > In[3]:=
Div[F] > > Out[3]= 0 > > The result should be 6, as it says in the
> book. I also get the result of 0 using > the Grad[] and Curl[] functions,
no matter > what they are acting on. Any ideas? > Sorry I missed this
the first time! If you type In[2] := ??Cartesian Mathematica will
tell you that the default coordinate variables are Xx, Yy, Zz. If
you do In[3] := Div[ {7 Xx, 0, -Zz} ] you will get the right answer.
When I looked in my copy of ''Guide to Standard Mathematica Packages'',
it sure looks like the variables are x, y, z, but then my copy is
Version 2.2. I assume that this was changed for 3.0. Robert

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