Rotation matrices
Consider the matrix
A = (cos t sin t)
(-sin t cos t)
Show that it is unitary
Show that the eigenvalues are exp(it) and exp(-it)
find the eigenvectors
Verify that U'AU is diagonal matrix, where U is the matrix of the eigenvectors.
Show that since determinant of a matrix is unchanged under unitary change of basis, argue that
1. det(A) = product of its eigenvalues for any Hermitian or Unitary A
2. use the invariance of teh trace under teh same transformation and show that Tr(A)= sum of eigenvalues
https://brainmass.com/physics/rotation/eigenvalues-eigenvectors-properties-matrix-201494
Solution Preview
see attached files.
The matrix is unitary since:
The eigenvevalues are the roots of the characteristic polynomial:
Which leads to the following eigenvalues:
The eigenvector associated with
The last two equations are actually the same, hence we can choose an arbitrary value for x and this will set up the value of y:
Thus ...
Solution Summary
The solution discusses some of the properties of general rotation matrices and show they are unitary matrices