proposition: Lemma mulR_eq0 (x y : R) : (x * y = 0) <-> ((x = 0) \/ (y = 0)).
proof: Proof. split => [/Rmult_integral //| [] ->]; by rewrite ?mul0R ?mulR0. Qed.
imports: mathcomp(all_ssreflect ssralg ssrnum) Reals mathcomp(lra) mathcomp(Rstruct)