Jordan's principal angles in complex vector spaces

We analyse the possible recursive definitions of principal angles and vectors in complex vector spaces and give a new projector based definition. This enables us to derive important properties of the principal vectors and to generalize a result of Björck and Golub (Math. Comput. 1973; 27(123):579–594), which is the basis of today’s computational procedures in real vector spaces. We discuss other angle definitions and concepts in the last section. Copyright q 2006 John Wiley & Sons, Ltd.