In other words its non-zero elements lie either on or immediately adjacent to the main diagonal. A is tridiagonal iff it is both upper and lower Hessenberg . A is also sometimes called an isometry . A real unitary matrix is called orthogonal .The following properties apply to orthogonal matrices as well as to unitary matrices. A H is unitary.
Unitary matrices are normal .
The eigenvalues of a unitary matrix all have an absolute value of 1. A matrix is unitary iff its columns form an orthonormal basis. Vandermonde matrices arise in connection with fitting polynomials to data.