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MathGroup Archive 2000

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Re: entering an equation

  • To: mathgroup at
  • Subject: [mg21603] Re: entering an equation
  • From: "Allan Hayes" <hay at>
  • Date: Sun, 16 Jan 2000 22:43:49 -0500 (EST)
  • References: <85s1gr$>
  • Sender: owner-wri-mathgroup at


The message tells you what the difficulty is for Mathematica.
It arrises since

Log[2,x] is complex for  x<0,  Indeterminate for x=0 (though it may be
defined as -Infinity),  negative for 0<x<1, zero for x =1, positive for x>1

Check by evaluating

Table[{x, Log[2, Log[2, x]]}, {x, -1, 2, .2}] // ColumnForm

"Mark Woolard" <mark at> wrote in message
news:85s1gr$ajj at
> I am trying to plot a series of functions in is giving
> 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?

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