Ask Your Question

# How should I get symbolic expression of eigenvalues and eigenvectors of a real symmetric matrix 3x3

Hi all I am a physicist and a new user of Sage. I used the following command on "Sage Version 5.1, Release Date: 2012-07-09", to get the expression of eigenvalue and eigenvectors of the symmetric real 3x3 matrix.

var('g11,g12,g13,g22,g23,g33',domain='real')
gamma=matrix(3,3,[g11,g12,g13,g12,g22,g23,g13,g23,g33])
eigs=gamma.eigenvectors_right()


It seems that this type of expression is unavailable, as it took forever to calculate on my laptop (Intel core i7) . So I would like to ask if I used the wrong command or mathematically the analytical expression is unavailable. Thanks very much.

edit retag close merge delete

## 1 Answer

Sort by » oldest newest most voted

You can access the documentation for eigenvalues_right:

sage: gamma.eigenvectors_right?


or the source code:

sage: gamma.eigenvectors_right??


There you see that the right eigenvectors are computed by computing the left eigenvectors of the transpose matrix. So let's check the documentation for eigenvectors_left:

sage: gamma.eigenvectors_left?


or the source code:

sage: gamma.eigenvectors_left??


You can see there an example involving a 2x2 matrix with symbolic entries, followed by the following comment:

This routine calls Maxima and can struggle with even small matrices
with a few variables, such as a 3\times 3 matrix with three variables.
However, if the entries are integers or rationals it can produce exact
values in a reasonable time.


Note: to get the documentation for that command in html format, do:

sage: browse_sage_doc(gamma.eigenvectors_left)

more

## Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

## Stats

Asked: 2014-02-16 20:24:10 +0200

Seen: 1,088 times

Last updated: Feb 17 '14