Re: entering an equation

• To: mathgroup at smc.vnet.net
• Subject: [mg21629] Re: [mg21592] entering an equation
• From: "Tomas Garza" <tgarza at mail.internet.com.mx>
• Date: Tue, 18 Jan 2000 02:35:16 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```Mark Woolard [mark at ratbyte.com] wrote:

> I am trying to plot a series of functions in Mathematica...one is
> giving me
> trouble. I need : ln2 (ln2 x)
>
>     I enter: Log[2, Log[2,x]]
>
> and I get:
>
> is not a machine-size real \
> number at \!\(x\) = \!\(4.1666666666666667`*^-7\)."
>
> Does anyone have any suggestions?

Yes. The range over which you wish to plot is important. Try, for example:

In[1]:=
Plot[Log[2, Log[2, x]], {x, 1, 2}]

The plot is OK. Look at the values of ln2 (ln2 x) in the neighborhood of 1 +
0:

In[2]:=
Table[Log[2, Log[2, x]], {x, 1, 2, 0.1}]
Out[2]=
{-Infinity, -2.86246, -1.92668, -1.40159, -1.04267, -0.773584, -0.56049, \
-0.38546, -0.237869, -0.110917, 0.}

Tomas Garza
Mexico City

```

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