proposition: Lemma normal_mx_ortho p (A : 'M_(p, n)) : (A _|_ (A^_|_)).
proof: Proof. by rewrite normalC. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg fingroup zmodp poly ssrnum) mathcomp(matrix mxalgebra vector falgebra ssrnum algC algnum) mathcomp(fieldext) mathcomp(vector)