(vi)
Identity matrix
A square matrix in which elements in the diagonal are all 1 and rest are all zero
is called an identity matrix In other words, the square matrix A = [aij] n × n is an
identity matrix, if 
1
0if
if
ij
i
j
a
i
j
=
= 
≠
 We denote the identity matrix of order n by In When order is clear from the
context, we simply write it as I