proposition: Lemma mx_normN x : mx_norm (- x) = mx_norm x.
proof: Proof. congr (_%:nngnum). by apply eq_bigr => /= ? _; apply/eqP; rewrite mxE -num_eq //= normrN. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrint ssrnum finmap matrix) mathcomp(rat interval zmodp vector fieldext falgebra) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality set_interval Rstruct) ereal reals signed topology prodnormedzmodule