The eigenvalues of a triangular or diagonal matrix are its diagonal elements. The eigenvalues of A have unit modulus. The geometric multiplicity of an eigenvalue is less than or equal to its algebraic multiplicity . The eigenvalues of a diagonal matrix equal its diagonal elements. If the off-diagonal elements are small rather than being exactly zero, the eigenvalues will be close to the diagonal elements.
Similar matrices have the same minimum polynomial.
The minimum polynomial of A is a factor of its characteristic polynomial .