From: Rob Biedenharn Date: 2011-05-13T03:53:42+09:00 Subject: Re: Math cube root On May 12, 2011, at 2:30 PM, Josh Cheek wrote: > On Thu, May 12, 2011 at 10:26 AM, Colin Bartlett >wrote: > >> On Thu, May 12, 2011 at 2:54 PM, serialhex >> 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! >> >> > 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 Rob@AgileConsultingLLC.com http://AgileConsultingLLC.com/ rab@GaslightSoftware.com http://GaslightSoftware.com/