Re: Writing a real valued expression in a form that does not include sqrt(-1)

From: "G. A. Edgar" <edgar@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Sun, 11 May 2008 13:41:02 -0400

In article
<7098b082-0bb8-4f1d-9d1c-3396dab824ea@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Szabolcs <szhorvat@xxxxxxxxx> wrote:

I was wondering if the following real-valued expression (obtained with
a CAS) could be written in a form that does not include the imaginary
unit (denoted by i here). I would like to do this without using
trigonometric functions (actually this expression is equal to cos(pi/
9))

(1/2)*((1 + i*sqrt(3))/2)^(1/3) + (4*(1 + i*sqrt(3)))^(-1/3)

Is this possible?

casus irreducibilis

http://en.wikipedia.org/wiki/Casus_irreducibilis

--
G. A. Edgar http://www.math.ohio-state.edu/~edgar/
.

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Re: Writing a real valued expression in a form that does not include sqrt(-1)
... On Sun, 11 May 2008, Szabolcs wrote: ... with a CAS) could be written in a form that does not include the ... imaginary unit. ...
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Re: Writing a real valued expression in a form that does not include sqrt(-1)
... Szabolcs wrote: ... a CAS) could be written in a form that does not include the imaginary ... blindly relies on CASs instead of learning something about 3rd order ...
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