proposition: Lemma formee i j : '['e_i, 'e_j] = M i j.
proof: Proof. rewrite /form -rowE -map_trmx map_delta_mx -[M in LHS]trmxK. by rewrite -tr_col -trmx_mul -rowE !mxE. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg fingroup zmodp poly ssrnum) mathcomp(matrix mxalgebra vector falgebra ssrnum algC algnum) mathcomp(fieldext) mathcomp(vector)