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MathGroup Archive 1997

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Q:SetCoordinates[system] usage

  • To: mathgroup at smc.vnet.net
  • Subject: [mg7651] Q:SetCoordinates[system] usage
  • From: sergio at scisun.sci.ccny.cuny.edu (Sergio Rojas)
  • Date: Tue, 24 Jun 1997 03:36:16 -0400 (EDT)
  • Organization: City College Of New York - Science
  • Sender: owner-wri-mathgroup at wolfram.com

Hello guys,

(*

  I have the following sequence in Mathematica

In[3]:= $Version

Out[3]= DEC OSF/1 Alpha 2.2 (September 9, 1994)

*)

Needs["Calculus`VectorAnalysis`"];

a = {Derivative[1, 0][PHI][r, phi], Derivative[0, 1][PHI][r, phi]/r, 0}
b = {0, 0, 1}

aXb = Simplify[CrossProduct[a,b]]

                                                (**********************

 In this form, aXb has the expected value:


             (0,1)
          PHI     [r, phi]      (1,0)
Out[20]= {----------------, -PHI     [r, phi], 0}
                 r

                                                 ********************)

(* However, by doing: *)

Clear[aXb];

SetCoordinates[Cylindrical[r,phi,z]];

aXb = Simplify[CrossProduct[a,b]]


                                                (**********************
  aXb has the weird looking output:

                  (1,0)        2
Out[28]= {Sqrt[PHI     [r, phi] ],

                   (0,1)
                PHI     [r, phi]     (1,0)
>    ArcTan[Sin[----------------] PHI     [r, phi],
                       r

               (0,1)
            PHI     [r, phi]     (1,0)
>     -(Cos[----------------] PHI     [r, phi])], 0}
                   r

                                                 ********************)

(* Am I misusing SetCoordinates[Cylindrical[r,phi,z]] here ? *)

Rojas

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




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