fact: Definition normrMn V (x : V) n : `|x *+ n| = `|x| *+ n := normrMn x n.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)