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MathGroup Archive 1997

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Re: Wrong behavior of CrossProduct

  • To: mathgroup at smc.vnet.net
  • Subject: [mg8003] Re: Wrong behavior of CrossProduct
  • From: Sergio Rojas <sergio at scisun.sci.ccny.cuny.edu>
  • Date: Wed, 30 Jul 1997 23:57:57 -0400
  • Sender: owner-wri-mathgroup at wolfram.com


On Mon, 28 Jul 1997, Paul Abbott wrote:

> Sergio Rojas wrote:
> 
> > In[1]:= Needs["Calculus`VectorAnalysis`"];
> > In[2]:= SetCoordinates[Spherical[r,theta,phi]];
> > In[3]:= V = {a1,a2,0};
> > In[4]:= U = {0, 0, 1};
> > In[5]:=  CrossProduct[U,V]
> > Out[5]= {0, 0, 0}
> >                  (* Again, wrong result. Same results were obtained on *)
> 
> Why do you say this result is wrong?  Your vector U={0, 0,
> 1}=={r,theta,phi} has zero length.
> 

  However, according to Arfken's Mathematical Methods for Physicists, Third 
Edition, Pg. 88, equation 2.11b, the answer should be (a2,-a1,0). It has 
the same form as in Cartesian coordinates but with different meaning for 
the symbols a1 and a2.

Rojas

E-mail: sergio at scisun.sci.ccny.cuny.edu


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