proposition: Lemma fct_der4 : forall t : R, derivable_pt ((Rs * comp cos alphas_p)%F + fct_cte (xi intr 0)) t.
proof: Proof. intro; reg. apply (cond_D1 alphas). apply Rs_derivable. Qed.
imports: Reals trajectory_def trajectory_const constants ycngftys rrho