Definition G (t : R) : R := (Rs t - F t)%R.

Lemma D_G_alphas : forall t : R, (derive_pt G t (G_derivable t) * (derive_pt Rs t (Rs_derivable t) + derive_pt F t (F_derivable t)))%R = (- Rsqr (derive_pt alphas t (cond_D1 alphas t)) * G t * (Rs t + F t) + Rsqr (F t) * (Rsqr (rho (vi intr) / 2) - Rsqr (derive_pt alphas t (cond_D1 alphas t))))%R.