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