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In matrix theory, Sylvester's determinant theorem is a theorem useful for evaluating certain types of determinants. It is named after James Joseph Sylvester, who stated this theorem without proof in 1851.〔 Cited in 〕 The theorem states that if ''A'', ''B'' are matrices of size ''p'' × ''n'' and ''n'' × ''p'' respectively, then : where ''I''''a'' is the identity matrix of order ''a''.〔 page 416〕 This can be seen for invertible ''A'', ''B'' by conjugating ''I + AB'' by ''A−1'', then extended to arbitrary square matrices by density of invertible matrices, and then to arbitrary rectangular matrices by adding zero column or row vectors as necessary. It is closely related to the Matrix determinant lemma and its generalization. It is the determinant analogue of the Woodbury matrix identity for matrix inverses. ==Proof== The theorem may be proven as follows.〔.〕 Let be a matrix comprising the four blocks , , and :. Block LU decomposition of yields : from which : follows. Decomposing to an upper and a lower triangular matrix instead, :, yields :. This proves :. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Sylvester's determinant theorem」の詳細全文を読む スポンサード リンク
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