proposition: Lemma mcoeffX m k : 'X_[m]@_k = (m == k)%:R.
proof: Proof. by rewrite unlock /mpolyX_def mcoeff_MPoly coeffU mul1r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(order fingroup perm ssralg zmodp poly ssrint) mathcomp(matrix vector) mathcomp(bigenough) ssrcomplements freeg