proposition: Lemma mul_kermx m n (M : 'M_(m, n)) : kermx M *m M = 0.
proof: Proof. rewrite -{2}[M]mulmx_ebase !mulmxA mulmxKV ?col_ebase_unit //. by rewrite mul_copid_mx_diag ?mul0mx // geq_min /mxrank leqnn orbT. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path tuple) mathcomp(perm fingroup choice ssralg fintype finfun poly polydiv) mathcomp(bigop matrix zmodp mxalgebra) ssrcomplements dvdring mxstructure similar minor binetcauchy stronglydiscrete coherent