  Rays are classes of an equivalence relation on a module V over a
supertropical semiring. They provide a version of convex geometry, supported by
a "supertropical trigonometry" and compatible with quasilinearity, in which the
CS-ratio takes the role of the Cauchy-Schwarz inequality. CS-functions which
emerge from the CS-ratio are a useful tool that helps to understand the variety
of quasilinear stars in the ray space Ray(V). In particular, these functions
induce a partition of Ray(V) into convex sets, and thereby a finer convex
analysis which includes the notions of median, minima, glens, and polars.
