Properties Of The Product Of Two Orthogonal Projection Operators

Operator theory is an important branch of functional analysis.The main research object of functional analysis is space and mapping.What we call operators usually refer to the mapping of infinite dimensional space.Because of its wide application,it has been received by many scholars.The main research object of this paper is the orthogonal projection operator.The CS decomposition method is used to study the necessary and sufficient conditions for the product of two orthogonal projection operators to be a co-EP operator,an EP operator,a hypo-EP operator,a self-conjugate operator,a normal operator,a partial isometric operator,and a orthogonal projection operator.