MathGroup Archive 2002

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RE: Curl

  • To: mathgroup at smc.vnet.net
  • Subject: [mg34902] RE: [mg34875] Curl
  • From: "David Park" <djmp at earthlink.net>
  • Date: Wed, 12 Jun 2002 02:15:34 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

John,

Very simple. Multiplication of two symbols is indicated either by leaving a
space between them or putting an * between them. x z is x times z. x*z is x
times z. But xz is a new symbol with no relation to x or z.

If you write your products correctly, you will obtain the expected answer.

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/

> From: John Deacon [mailto:jdeacon at jdl.co.uk]
To: mathgroup at smc.vnet.net
>
>
> I must be getting the coordinate system wrong. I want to
> calculate something like curl F where
>  F(x,y,z) = ixz + jyz + ky^2
> where i, j and k are the unit vectors in the x, y and z
> directions respectively.
>
> 	<< Calculus`VectorAnalysis`
> 	SetCoordinates[Cartesian[x, y, z ]]
> 	Curl[{xz, yz, -y^2}]
> produces
> 	{-2 y, 0, 0}
> Yet I would swear it should be -3yi + xj
>
> What am I doing wrong?
>
> John
>
>
>



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