Computation of cofactors of [sI-A] with applications

The cofactors of
[sI-A]
are the key to accurate, efficient calculation of
[sI- A]^{-1}
and
\partial \lambda/\partial a_{ij}
, where a
ij
is an element of
A
. These cofactors can be evaluated by transforming their equivalents to phase variable or quasi-phase variable form. The procedure for forming the equivalent cofactors is the principal topic of this note.