proposition: Lemma BQprod_cN a b: natp a -> natp b -> BQ_of_nat (a *c b) = BQ_of_nat a *q (BQ_of_nat b).
proof: Proof. move => aN bN; rewrite /BQ_of_nat. by rewrite (BQprod_cZ (BZ_of_nat_i aN) (BZ_of_nat_i bN)) (BZprod_cN aN bN). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)