proposition: Fact addfxC : commutative subfext_add.
proof: Proof. by move=> x y; rewrite -[x]reprK -[y]reprK !piE addrC. 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)