# [Maxima] eigenvalue, eigenvector

Raymond Toy (RT/EUS) raymond.toy at ericsson.com
Wed May 28 12:39:19 CDT 2008

```ahmet alper parker wrote:
> Dear all,
> I have a K matrix as
> K:matrix([(12*E*I)/L^3,0,0],[0,(3.555555555555555*E*I)/L^3,-(3.555555555555555*E*I)/L^3],[0,-(3.555555555555555*E*I)/L^3,(7.111111111111111*E*I)/L^3]);
> and an M matrix as
> M:matrix([(m*L)/2,0,0],[0,(5*m*L)/4,0],[0,0,(3*m*L)/2]);
> and I am trying to solve
> (K-w^2*M)*f=0 eigenvalue problem. (Solving for w eigenvalue and f
> eigenvector)
> When making manually by equating the determinant to zero and solving for
> w, I get the w correct. But when I tried to solve for f, I got different
> answers depending on the method I choose,
> First solving as a linear equation with 3 equations I get one set of
> eigenvectors,
> Second, first eigenvector's first term is zero. I get the first equation
> out of the system and solved for the rest two equations, I get different
> eigenvectors,
> Also, they are not proportional, I mean taking one of the eigenvector
> values as unity makes the other some value, however taking the other as
> unit makes the other another different value, in which I cannot properly
> unitize them. I mean, if I take the second value of the eigenvector 1 ,
> the other (third) is say 0.5 however, if I take the third as 1 it does
> not make the second 2.

I'm thoroughly confused by what you're saying here.  Can you show what
you're actually doing?

Ray
```