MATLAB: Symbolic calculation

Question

Hi, consider following commands:

syms a b c;
A=[a b;b c];
[R1,e]=eig(A);
rhs=matlabFunction(R1);

Now I would like to calculate the eigenvalue of [1 2;2 3], So I write:

[Rn,en]=eig([1 2;2 3])

Result in this case is:

Rn =
   -0.8507    0.5257
    0.5257    0.8507

But if I use symbolic formula:

rhs(1,2,3)
ans =
   -1.6180    0.6180
    1.0000    1.0000

Why are they different? What is wrong with my calculation?

Answer 1

You are comparing eigenvectors, which need not be unique.

Comparing eigenvalues:

rhs = matlabFunction(e);
rhs(1,2,3)
en