       Re: simple Problem: D[ ]

• To: mathgroup at smc.vnet.net
• Subject: [mg27325] Re: simple Problem: D[ ]
• From: Albert Retey <albert.retey at visualanalysis.com>
• Date: Wed, 21 Feb 2001 03:16:56 -0500 (EST)
• Organization: Visual Analysis AG
• References: <96t91a\$pqt@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Christian Maier wrote:
>
> 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!
>
> Christian Maier

f[x]:=x^2

This should do what you want, the colon will cause the left hand side to
be
evaluated only, when the "pattern" f[x] will be met. For a real
"function definition" with arbitrary argument you should use:

f[x_]:=x^2

Then even D[f[y],y] should work the way you expect it. Nevertheless, try
to first read some introduction to Mathematica, for a beginning the
first chapter in the online help -> the mathematica book should do.

Albert
--
Visual Analysis AG       Internet: www.visualanalysis.com
Neumarkter Str. 87       Telefon: 089 / 431 981 36
D-81673 Muenchen         Telefax: 089 / 431 981 1

```

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