Definition double_round_sqrt_hyp fexp1 fexp2 :=
  (forall ex, (2 * fexp1 ex <= fexp1 (2 * ex))%Z)
  /\ (forall ex, (2 * fexp1 ex <= fexp1 (2 * ex - 1))%Z)
  /\ (forall ex, (fexp1 (2 * ex) < 2 * ex)%Z ->
                 (fexp2 ex + ex <= 2 * fexp1 ex - 2)%Z).

Lemma FTZ_double_round_sqrt_hyp : (2 * (emin' + prec') <= emin + prec <= 1)%Z -> (2 * prec + 2 <= prec')%Z -> double_round_sqrt_hyp (FTZ_exp emin prec) (FTZ_exp emin' prec').