On Sun, Mar 28, 2010 at 12:35 PM, Owen <[email protected]> wrote:
> I'd like to have the result of a sage calculation somehow remain as an
> irrational fraction.  Specifically, here I'm calculating the
> eigenvalues of the matrix who's powers generate the fibonacci numbers:
> sage: m=matrix(2,2,[0,1,1,1]);m
> [0 1]
> [1 1]
> sage: m.eigenvalues ()
> [-0.618033988749895?, 1.618033988749895?]
>
> I'd LOVE to be able to somehow get the more meaningful value of which
> contains the 1+/-sqrt(5) form:

Just use SR = SymbolicRing():

sage: m=matrix(SR,2,2,[0,1,1,1]);m
[0 1]
[1 1]
sage: m.eigenvalues()
[-1/2*sqrt(5) + 1/2, 1/2*sqrt(5) + 1/2]


>
> sage: n=(1+sqrt(5))/2;n
> 1/2*sqrt(5) + 1/2
> sage: N(n)
> 1.61803398874989
>
> Is there some way I can ask for the eigenvalues (or any other roots)
> in such a format?
>
> [This is pretty noob, I realize, but I tried several searches, and
> even found golden-ratio, but couldn't figure out how to achieve the
> desired result of not evaluating irrationals]
>
> Thanks!  Sage rocks!

+100

>
>   -- Owen
>
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-- 
William Stein
Associate Professor of Mathematics
University of Washington
http://wstein.org

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