In this note
we find an explicit expression for the eigenvalues of a
retarded time-delay system with one delay, for the special case that the system matrices are
simultaneously triangularizable,
which includes the case
where they commute. Using matrix
function definitions
we define a matrix version of the
Lambert w the MathML source">W function, from
which
we form the expression. We prove by counter-example that some expressions in other publications on Lambert
w the MathML source">W for time-delay systems do not al
ways hold.