proposition: Lemma mcoeffXU (i j : 'I_n) : ('X_i : {mpoly R[n]})@_U_(j) = (i == j)%:R.
proof: Proof. by rewrite mcoeffX eq_mnm1. 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