| Author |
Comment/Response |
Robert Astalos
|
 01/20/97 6:07pm
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? > Lars, The other
way to use this function is: In[1] := Div[ {7 x, 0, -z}, Cartesian]
Unfortunately, this also gives 0. But when I explicitly state the
coordinates, it does it right: In[2] := Div[ {7 x, 0, -z}, Cartesian[x,
y, z] ] Out[2] = 6 This leads me to believe that the ''default'' coordinate
system (supposedly Cartesian(?)) uses some other letters to designate
it's axes, or maybe it MUST be told explicitly what letters you are
using. Could this be a change from version 2.2? Robert
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