Re: Derivative
- To: mathgroup@smc.vnet.net
- Subject: [mg12334] Re: Derivative
- From: A Hayes <hay@haystack.demon.co.uk>
- Date: Thu, 7 May 1998 18:52:20 -0400
- References: <6imi8n$h01@smc.vnet.net>
Il prof wrote:
>
> Has anybody an idea of how to implement an algorithm for calculating
> symbolic derivatives?
> Any help will be appreciate
>
> thank you
>
> rvalente @ iol.it
Of course Mathematica has this built in.
(1)
If you want to do it yourself then to begin with you can simply write
the elementary rules:
d[expr_, x_]/;FreeQ[expr,x] := 0 (*when expr is free of x*) d[x_,x_] :=
1
d[a_ + b_, x_] := d[a,x] + d[b,x]
d[a_ b_, x] := d[a, x] b + a d[b, x] d[a_^n_,x_]/;FreeQ[n,x] := n
a^(n-1) d[a,x]
We could go on, but let's apply the rules so far entered.
d[3 x^4 - 1/(2- a x^3)^2, x]
2
3 6 a x
12 x - -----------
3 3
(2 - a x )
Check against the built in differentiating function.
D[ 3 x^4 - 1/(2- a x^3)^2, x]
2
3 6 a x
12 x - -----------
3 3
(2 - a x )
(2) Check out George Beck's notebook Step-by-Step Differentiation in the
Help Browser: Getting Started/Demod | Demos | Notebook Demos
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Allan Hayes
Training and Consulting
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