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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