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MathGroup Archive 2004

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Re: Recursion Limit & Symbolic Differentiation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg52265] Re: [mg52258] Recursion Limit & Symbolic Differentiation
  • From: yehuda ben-shimol <benshimo at bgu.ac.il>
  • Date: Sat, 20 Nov 2004 03:41:33 -0500 (EST)
  • References: <200411180644.BAA10625@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Since you did not send the function and how you try to differentiate it 
I'm submitting a basic response
Say your function is defined as
f[x_,y_,z_]:=Sin[x y z];
Use Dt for total derivative
Dt[f[x, y, z]]
and get
Cos[x y z] (y z Dt[x] + x z Dt[y] + x y Dt[z])
This assumes that x, y and z may be functions of other variables

For partial derivatives use D[ ], for example differentiate the given 
Sin[x y z] according to x
D[f[x, y, z], x]
and get
y z Cos[x y z]

I know this is VERY basic but I hope this helps
yehuda


Erin wrote:

>Hi,
>
>I'm new to Mathemtica and I'm trying to differentiate a multi-variable
>function 
>f(x,y,z). When doing so I get a recusion limit 256 reached message. 
>
>When examining my equations, I don't see recursion in the expressions.
>It should be simple substitution of one expression into the other.
>(Its just easier for me to write it that way). 
>
>How do I know if this is a valid message, and how do I know if my
>expressions will actually be solved / simplified by Mathematica if I
>increase the recursion limit?
>
>I have 2GB RAM and Mathematica fills it, then the Kernel runs out of
>memory and stops trying to solve the problem. 
>
>Thanks.
>
>  
>


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