(*********************************************************)
(** ** Square function                                   *)
(*********************************************************)

Definition Rsqr r : R := r * r.Notation "r ²" := (Rsqr r) (at level 1, format "r ²") : R_scope.

Lemma Ropp_ge_contravar : forall r1 r2, r2 >= r1 -> - r1 >= - r2.