 Weinstein–Aronszajn identity

In mathematics, the Weinstein–Aronszajn identity states that if formula_1 and formula_2 are matrices of size and respectively (either or both of which may be infinite) then,
provided formula_3 is of trace class (and hence, so is formula_4),

where formula_6 is the identity matrix.It is closely related to the Matrix determinant lemma and its generalization.