Definition alphas_p : R -> R := d2 alphas.

Lemma D_Rs_alphas2 : forall t : R, derive_pt (fun y : R => (Rs y * derive_pt alphas y (cond_D1 alphas y))%R) t (fct_der5 t) = (vi intr * cos (thetat t - alphas t) * (derive_pt thetat t (thetat_derivable t) - derive_pt alphas t (cond_D1 alphas t)))%R.