proposition: Fact addfxN : left_inverse subfext0 subfext_opp subfext_add.
proof: Proof. by move=> x; rewrite -[x]reprK !piE addNr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype tuple finfun bigop ssralg countalg) mathcomp(finalg zmodp matrix vector falgebra poly polydiv) mathcomp(mxpoly generic_quotient)