Re: Writing a real valued expression in a form that does not include sqrt(-1)
- From: Szabolcs <szhorvat@xxxxxxxxx>
- Date: Sun, 11 May 2008 11:00:49 -0700 (PDT)
On May 11, 7:41 pm, "G. A. Edgar" <ed...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
In article
<7098b082-0bb8-4f1d-9d1c-3396dab82...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Szabolcs <szhor...@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
Ah, thanks for the pointer. This is what happens when one just
blindly relies on CASs instead of learning something about 3rd order
equations.
The equation was:
-(1/2) - 3*x + 4*x^3 == 0
.
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