$$A = \left[ \begin{array} { l l } { \tan \theta } & { \sec \theta } \\ { \sec \theta } & { \tan \theta } \end{array} \right] A ( a d j A ) = \left[ \begin{array} { l l } { k } & { 0 } \\ { 0 } & { k } \end{array} \right] k =$$
