1. Sep 1, 2009

### Charles007

I know how to find the adjugate of 3x3 matrix. from the defination.

How to find adjugate of 2x2 matrix.

e.g A= ( 1 3 )
______( 2 4 )

First . we find matrix of cofactor. from the defination. (n-1)(n-1) matrix * (sign associated with the element's position).

Second, we taking the transpose we get the adj(A)

Then we find the det(A).

Finally, A^-1 = 1/det(A) * adj(A)

The inverse of A.

$AA^- = A^-A=I$ and A adj(A) = det(A)I

The inverse of $A = det(A)I/ A^-$

Last edited: Sep 1, 2009