Re: Almost symbolic computations (?)
- To: mathgroup at smc.vnet.net
- Subject: [mg90505] Re: [mg90466] Almost symbolic computations (?)
- From: DrMajorBob <drmajorbob at att.net>
- Date: Fri, 11 Jul 2008 02:03:25 -0400 (EDT)
- References: <24624830.1215688345875.JavaMail.root@m08>
- Reply-to: drmajorbob at longhorns.com
The tutorial at "VectorAnalysis/tutorial/VectorAnalysis" says, "The
initial default coordinate system is Cartesian, with coordinate variables
Xx, Yy, and Zz."
So you didn't use proper variables.
Your specific problem:
Curl[{a x, a y, a z}, Cartesian[x, y, z]]
{0, 0, 0}
should be a special case of
Curl[{f[x, y, z], g[x, y, z], h[x, y, z]}, Cartesian[x, y, z]]
{-(g^(0,0,1))[x,y,z]+(h^(0,1,0))[x,y,z],(f^(0,0,1))[x,y,z]-(h^(1,0,0))[x,y,z],-(f^(0,1,0))[x,y,z]+(g^(1,0,0))[x,y,z]}
A little visual inspection confirms it.
Bobby
On Thu, 10 Jul 2008 05:35:14 -0500, Barbara Da Vinci
<barbaradavinci at tahoo.it> wrote:
> Dear MathGroup
>
> This is an example of the problem
> I'm facing.
>
> The code
>
> Needs["VectorAnalysis`"];
> Head /@ {ax, ay, az}
> A = {ax, ay, az};
> Curl[A]
>
> returns
>
> {Symbol, Symbol, Symbol}
> {0, 0, 0}
>
> Instead, I would get the
> well known symbolic form
>
> d_y az - d_z ay
> ...
>
> I have been trying, for
> a while, to perform string
> manipulations but that,
> of course, lays to ashes
> the possibility to recognize
>
> d_y az + d_y az = 2 d_y az
>
> and so on.
>
> Any way to get out of it ?
>
> Kind regards
>
>
> Barbara Da Vinci
>
>
--
DrMajorBob at longhorns.com