       Re: Re: Derivative of a funtion evaluated at a point in 3D

• To: mathgroup at smc.vnet.net
• Subject: [mg44474] Re: [mg44468] Re: Derivative of a funtion evaluated at a point in 3D
• From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
• Date: Wed, 12 Nov 2003 08:01:25 -0500 (EST)
• References: <boign7\$oj1\$1@smc.vnet.net> <200311110055.TAA25212@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```I guess nobody answered you because everyone expected someone else to
do so. The answer is pretty trivial, in Mathematica you don't define a
function by:

>> F[p1,p2,p3,p4] = stuff

but by

F[p1_,p2_,p3_,p4_] = stuff

You then use

D[F[p1,p2,p3,p4],p1] to get the first derivative with respect to p1,
D[F[p1,p2,p3,p4],{p1,2}] to get the second and so on. I am afraid there
are no shortcuts in Mathematica and you just have to learn the basics
yourself.

Andrzej Kozlowski

On 11 Nov 2003, at 09:55, mroc wrote:

> mroc_1000 at hotmail.com (mroc) wrote in message
> news:<boign7\$oj1\$1 at smc.vnet.net>...
>> Hello, I am totally new to Mathematica and trying to program a simple
>> FEM-type problem. I am trying to take the partial derivative
>> (symbolically) of an expression that is a function of four points in
>> 3D. All I can think of to do is F[p1,p2,p3,p4] = stuff then
>> D[F,p1,p2,p3,p4] . But I keep getting a zero expression as a result.
>> (where stuff is a nasty combination of these points) Any thoughts?
>
> Anyone? What am I missing? Is this question too easy or too hard?
>
>
>

```

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