Definition r_ub (h : TypeSpeed) : R := (h / rho_lb h)%R.Definition r_lb (h : TypeSpeed) : R := (h / rho_ub h)%R.

Lemma rho_strict_decreasing : forall h1 h2 : TypeSpeed, (h1 < h2)%R -> (rho h2 < rho h1)%R.