proposition: Lemma dvdr_coprime a b : a %| b -> coprimer a b -> a %= 1.
proof: Proof. move=> ab cab; rewrite -(eqd_rtrans cab) eqd_def dvdr_gcdl andbT. by rewrite dvdr_gcd dvdrr. Qed.
imports: HB(structures) Coq(ssreflect ssrfun ssrbool Arith.Wf_nat) mathcomp(eqtype ssrnat div seq path) mathcomp(ssralg fintype perm tuple choice generic_quotient) mathcomp(matrix bigop zmodp mxalgebra poly) stronglydiscrete