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

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

Lemma Rplus_npos_neg : forall r1 r2, r1 <= 0 -> r2 < 0 -> r1 + r2 < 0.