The identity matrix
2.6
The identity matrix of order n is the
n ? n matrix In=[aij], where aij=1 if i=j
and aij=0 if i ?j.
1 0 0 0 0
0 1 0 0 0
I5 = 0 0 1 0 0
0 0 0 1 0
0 0 0 0 1
If A is an m ? n matrix, then AIn= ImA = A.
2 3 5 7 8 1 0 0 0 0 2 3 5 7 8
1 0 3 2 6 ? 0 1 0 0 0 = 1 0 3 2 6
0 0 1 0 0
0 0 0 1 0
0 0 0 0 1
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