The points where the root loci intersect the imaginary axis of the s-plane, and the corresponding
values of K, may be determined by means of the Routh-Hurwitz criterion. For
complex situations, when the root loci have multiple number of intersections on the imaginary
axis, the intersects and the critical values of K can be determined with the help of
the root-locus computer program. The Bode diagram method in Chapter 9, associated with
the frequency response, can also be used for this purpose.