DLA Terminology and notation

Section 5.2 Terminology and notation

identity matrix: a square matrix with ones down the main diagonal and zeros everywhere else, usually represented by the letter $I$
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Remark 5.2.1.

There are many identity matrices, one of every possible size of square matrix. But we still often say the identity matrix, because we are usually referring to the identity matrix of a particular size. If we need to be clear about what size of identity matrix, we will write

I_{n}

to mean the

n \times n

identity matrix.

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inverse (of a square matrix $A$ ): a square matrix $B$ of the same size as $A$ so that both $B A = I$ and $A B = I$ are true, where $I$ is the identity matrix of the same size as $A$ and $B$
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invertible matrix: a square matrix for which an inverse exists
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singular matrix: a square matrix for which no inverse exists
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