From: jzakiya <jzakiya@...>
Date: 2011-05-13T05:25:49+09:00
Subject: Re: Math cube root

On May 12, 2:53 pm, Rob Biedenharn <R...@AgileConsultingLLC.com>
wrote:
> On May 12, 2011, at 2:30 PM, Josh Cheek wrote:
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> > On Thu, May 12, 2011 at 10:26 AM, Colin Bartlett <colin...@googlemail.com
> > >wrote:
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> >> On Thu, May 12, 2011 at 2:54 PM, serialhex <serial...@gmail.com>  
> >> wrote:
> >>> ...
> >>> instead of using floats you can try to use rational numbers in ruby:
> >>> ruby-1.9.2-p180 :001 > require 'mathn'
> >> which also changes this:
> >> (-1) ** (1.0 / 3) #=> NaN
> >> to:
> >> (-1) ** (1.0 / 3) #=> (0.5+0.866025403784439i)
> >> so we can also get complex roots if we want them!
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> > Which we don't here, given that the cube root of -1 isn't imaginary :/
>
> ONE of the cube roots of -1 isn't imaginary, but the other two are.  
> Since (1.0/3) isn't exactly one-third, raising -1 to (1.0/3) isn't  
> exactly the same as taking the cube root either.
>
> -Rob
>
> Rob Biedenharn          
> R...@AgileConsultingLLC.com  http://AgileConsultingLLC.com/
> r...@GaslightSoftware.com            http://GaslightSoftware.com/

See my Roots Module.
https://gist.github.com/422636

It allows you to easily (and accurately) get all n values for a root
n,
for all number classes.

Instead of:  1000**3**-1  of 1000**(1.0/3) to get only default root
Instead do:  1000.root(3) or 1000.roots(3), for all 3 cube roots

Jabari Zakiya