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Re: entering an equation
*To*: mathgroup at smc.vnet.net
*Subject*: [mg21606] Re: [mg21592] entering an equation
*From*: BobHanlon at aol.com
*Date*: Sun, 16 Jan 2000 22:43:52 -0500 (EST)
*Sender*: owner-wri-mathgroup at wolfram.com
For the function Log[2, Log[2, x]] to be real, Log[2, x] must be positive.
Log[2, x] > 0
Log[x]/Log[2] > 0
That is,
Log[x] > 0;
or
x > Exp[0]
x > 1
Needs["Algebra`InequalitySolve`"]
InequalitySolve[Log[2, x] > 0, x]
InequalitySolve::npi A nonpolynomial equation or inequality encountered. The
solution set may be incorrect.
x > 1
Table[{x, Log[2, Log[2, x]]}, {x, 0., 1.5, .25}]
{{0., Indeterminate}, {0.25, 1. + 4.532360141827193*I},
{0.5, 0. + 4.532360141827193*I},
{0.75, -1.2686864028144482 + 4.532360141827193*I},
{1., Indeterminate}, {1.25, -1.6351896075841128},
{1.5, -0.773583951828313}}
Plot[Log[2, Log[2, x]], {x, 1, 10}];
Bob Hanlon
In a message dated 1/16/2000 5:18:21 AM, mark at ratbyte.com writes:
>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?
>
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