Inverse matrix proof
Let A =
be a non-singular matrix.
i.e, det(A) ≠ 0.
From the definition of invertible, A
– 1
exists.
Let A
1
, B
1
, C
1
..... C
3
be the cofactors of an elements a
1
, b
1
, c
1
..... c
3
respectively.