RE: What does power operator ^ returns?

[dastew]

> From: address@hidden
> Subject: What does power operator ^ returns?
> Date: Mon, 19 Oct 2009 16:42:06 +0000
> To: address@hidden
>
> Hi all!
>
> I need to compute the cubic root of many negative numbers. My problem
> is real-valued, hence I am not interested in the imaginary solutions.
> However, if I use the power operator '^', Octave returns just the
> first imaginary solution. The same applies when doing any odd root.
>
> Example:
> octave> a=-8
> a = -8
> octave> a^(1/3)
> ans = 1.000000000000000e+00 + 1.732050807568877e+00i
>
> How can I make octave to return the real solution, which in my example
> is just -2? I do not want just the absolute value (i.e. abs(a^(1/3)),
> since it does not preserve the sign. I could do with a check on the
> sign, but it would be inefficient.
>
> I am using Octave 3.2.3 on Mac Os X 10.6.
>
> Thank you very much,
>
> Guido
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if you want to see all the roots try

roots([1 0 0 8])

that will give you all the cube roots of -8

and roots([1 0 0 0 0 8])
will give you all 5,   fifth roots of -8  
:-)

Doug