For a Hermitian matrix, let be its th column without the diagonal entry and let . Solve the two block equations of the inverse against the th coordinate vector to obtain this formula. Both full and minor inverses must exist; nonreal guarantees that. In the real symmetric case may be replaced by .
Articles by others on the same topic
The Schur complement is a concept in linear algebra that arises when dealing with block matrices. Given a partitioned matrix, the Schur complement provides a way to express one part of the matrix in terms of the other parts.