An matrix (*square* matrix) of the form

Let be an matrix.
If there exists an matrix satisfying
and ,
then is said to be *invertible*,
and is called the inverse of ,
denoted by .
If is *not* invertible,
we call a *singular* matrix.

In Matlab/Octave
the function `eye(n)` generates the identity matrix.
For example,

> eye(5)creates the identity matrix.

EXAMPLE 1 Find and identity matrix.

Department of Mathematics