Re: RE:? D[f,{x,n}]
- To: mathgroup at smc.vnet.net
- Subject: [mg25571] Re: RE:[mg25495] ? D[f,{x,n}]
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Sun, 8 Oct 2000 00:41:58 -0400 (EDT)
- References: <8rmlm3$2i9@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Ted
Re your observation:
> this
> seems to prove that D[f, {x, n}] evaluates
> Nest[ D[#, x]&, f, n ]
> or something equivalent.
The following supports this.
x /: x^3 = a[x];
D[x^5, {x, 3}]
20*Derivative[1][a][x]
Derivative[3][Function[x, x^5]]
Function[x, 20*Derivative[1][a][x]]
But,
f[x_] := x^5;
Derivative[3][f][x]
60*x^2
--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
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