proposition: Lemma CTheory : ring_theory zeroC oneC Cplus Cmult Cminus Copp (eq(A:=C)).
proof: Proof. split. exact Cplus_zeroC_z. exact Cplus_commutative. exact Cplus_associative. exact Cmult_oneC_z. exact Cmult_commutative. exact Cmult_associative. exact Cmult_distributive_r. reflexivity. exact Cplus_z_oppz. Defined.