# Identity matrix

From Encyclopedia of Mathematics

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A square matrix $I$ with entries $1$ on the main diagonal and $0$ otherwise: $$ I_{ij} = \delta_{ij} $$ where $\delta$ is the Kronecker symbol.

It is the identity element in the matrix ring.

**How to Cite This Entry:**

Identity matrix.

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Identity_matrix&oldid=36228