Identity Matrix

What is an identity matrix?

An identity matrix is also called a unit matrix. An identity matrix is a square matrix in which:

• all the elements of the diagonal between the top left corner and the bottom right hand corner are ones and
• all the other elements are zeros.

Identify matrices

Below are example of identity matrices.

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Property of the identity matrix

The identity matrix is very useful because of the following property which you can assume for all identity matrices. If  I  represents the identity matrix and A is any other matrix, then:

Example of calculation with the identity or unit matrix