If 
show that A’A = I.
Given 
, We will find A’
LHS = A’A
[Using 
and commutative law a.b = b.a i.e. 
]
RHS = I 
LHS = RHS
Hence proved.
1
If show that A’A = I.
Given , We will find A’
LHS = A’A
[Using and commutative law a.b = b.a i.e. ]
RHS = I
LHS = RHS
Hence proved.