proposition: Lemma eqCmod_trans e y x z : (x == y %[mod e] -> y == z %[mod e] -> x == z %[mod e])%C.
proof: Proof. by move=> Exy Eyz; rewrite /eqCmod -[x](subrK y) -[_ - z]addrA rpredD. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun ssrnat eqtype seq choice) mathcomp(div fintype path bigop finset prime order ssralg) mathcomp(poly polydiv mxpoly generic_quotient countalg) mathcomp(ssrnum closed_field ssrint archimedean rat intdiv) mathcomp(algebraics_fundamentals)