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 > > >