Qed.
(**********)
Axiom
G_pos :
forall t : R, (0 <= t)%R -> (t < 2 / rho (vi intr))%R -> (0 <= G t)%R.
(**************************)
(******* THEOREM **********)
(**************************)

Theorem YCNGSTYS :
forall t : R,
(0 <= t)%R ->
(rho (vi intr) * t < 2)%R ->
(2 * r (vi intr) * sin (rho (vi intr) * (t / 2)) <=
sqrt (Rsqr (xi intr t - xi intr 0) + Rsqr (yi intr t - yi intr 0)))%R.