Cofactor/Examples/Arbitrary Example 2

Example of Cofactor
Let $D$ be the determinant defined as:


 * $D = \begin {vmatrix} a_{11} & a_{12} & a_{13} \\

a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} & a_{33}\end {vmatrix}$

Then the cofactor of $a_{2 1}$ is defined as: