       Re: Derivative help

• To: mathgroup at smc.vnet.net
• Subject: [mg39468] Re: Derivative help
• From: Paul Abbott <paul at physics.uwa.edu.au>
• Date: Mon, 17 Feb 2003 04:34:51 -0500 (EST)
• Organization: The University of Western Australia
• References: <b1dg35\$7ar\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```In article <b1dg35\$7ar\$1 at smc.vnet.net>,
"Steve Chiang" <stevezx at attbi.com> wrote:

> Hi, all.  I'm new to Mathematica.  I went to the help section for my
> question but it only further confused me.  I'm basically trying to take the
> first derivative of (ln(x))^x.  Here is my syntax: f = (ln(x))^x.

In contrast to most responses in this thread this syntax is ok -- as
long as you use TraditionalForm for input (under the Cell menu | Default
Input FormatType). Personally I prefer TraditionalForm for input and
output.

> But then when I evaluate f ', it says nothing but ((ln(x))^x)' which is
> nothing new.

f = (ln(x))^x
D[f,x]

Alternatively, you can make f an explicit function of x,

Clear[f]
f[x_] = (ln(x))^x
f'[x]

or make f a pure function.

Clear[f]
f = Function[x, (ln(x))^x]
f'

Cheers,
Paul

```

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