TheoremBase

Rules for Matrix Inverses

The identity is its own inverse; a one-sided inverse of a square matrix is its inverse; inverses of inverses, products and transposes are given by the usual formulas; and Ax = b has the unique solution A−1bA^{-1}b.

Statement

In the setting of Metric Spaces: Balls, the Metric Topology, and the Real and Complex Numbers as Metric Spaces, let n∈Nn\in\mathbb{N} and A,B,C∈Mn(R)A,B,C\in\mathcal{M}_{n}(\mathbb{R}), square real matrices, with the matrix product, the matrix-vector product, the transpose, the identity matrix InI_{n}, invertible matrices and their inverses, and points of Rn\mathbb{R}^{n}.

InI_{n} is invertible and In−1=InI_{n}^{-1}=I_{n}.

If AC=InAC=I_{n} or CA=InCA=I_{n}, then AA is invertible and A−1=CA^{-1}=C.

If AA is invertible, then A−1A^{-1} is invertible and (A−1)−1=A(A^{-1})^{-1}=A.

If AA and BB are invertible, then ABAB is invertible and (AB)−1=B−1A−1(AB)^{-1}=B^{-1}A^{-1}.

If AA is invertible, then A⊤A^{\top} is invertible and (A⊤)−1=(A−1)⊤(A^{\top})^{-1}=(A^{-1})^{\top}.

If AA is invertible and b∈Rnb\in\mathbb{R}^{n}, then A−1bA^{-1}b is the only x∈Rnx\in\mathbb{R}^{n} with Ax=bAx=b.

Proofs

Log in to submit a proof.

Loading...

Citations

Loading…

Dependencies

Loading…

Related

0 relations

Curated associations between results. These are editable and subjective — they do not replace the dependency graph, which is derived from the references in the text.

No relations recorded yet.

Comments

Log in to comment.

Loading…