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Re: simple Problem: D[ ]

• To: mathgroup at smc.vnet.net
• Subject: [mg27337] Re: simple Problem: D[ ]
• From: "Paul Lutus" <nospam at nosite.com>
• Date: Wed, 21 Feb 2001 03:17:16 -0500 (EST)
• References: <96t91a$pqt@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

"Christian Maier" <maier1 at sbox.tu-graz.ac.at> wrote in message
news:96t91a$pqt at smc.vnet.net...
>
> I use mathmatica the first time and have a problem with a deriviation:
>
> in a simple problem:
>
> f[x]=x^2
> abl=D[f[x],x]
>
> then Mathematica puts out f[x]'    , but not 2 x
>
> How does it work correctly?
> Thank aou in advance!

You must write your function so that the "x" variable is correctly
identified as being passed to the expression at the right:

f[x_] := x^2


f'[x]

2 x

f''[x]

2

f'''[x]

0

If you have a relatively recent version of Mathematica, look in the
documentation under "1.7.1 Defining Functions"

--
Paul Lutus
www.arachnoid.com