Alec Mihailovs skryf:
>
> ----- Original Message -----
> From: "Dirk Laurie" <[EMAIL PROTECTED]>
> >
> > David Joyner skryf:
> >>
> >> Timothy Clemans wrote:
> >> > Does SAGE support finding the nth root of something?
> > > The cube root of 27 is 3, 8 is 2, 64 is 4
> >> >
> >>
> >> One way is
> >> ZZ(gap.eval("RootInt( 64, 3 )"))
> >>
> > Or:
> > (x^n-a).roots()[0][0]
>
> Or
> {{{
> sage: exp(log(64)/3)
> 4.0
> }}}
Well, that works for the cube root of 64. But note it's 4.0, not 4.
This exposes one to roundoff errors, which the other two methods
avoid.
sage: a=2^54
sage: b=(a-1)^3
sage: exp(log(b)/3)
_3 = 18014398509482004
sage: (x^3-b).roots()[0][0]
_4 = 18014398509481983
sage: a-1
_5 = 18014398509481983
Dirk
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to sage-support@googlegroups.com
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/sage-support
URLs: http://sage.math.washington.edu/sage/ and http://sage.scipy.org/sage/
-~----------~----~----~----~------~----~------~--~---
