proposition: Lemma lt0_norm_powR a x : a < 0 -> `|a `^ x| = 1.
proof: Proof. move=> a0; rewrite /powR lt_eqF// gtr0_norm ?expR_gt0//. by rewrite ln0 ?mulr0 ?expR0// ltW. Qed.
imports: mathcomp(all_ssreflect ssralg ssrint ssrnum matrix) mathcomp(interval rat) mathcomp(boolp classical_sets functions) mathcomp(mathcomp_extra) reals ereal signed topology normedtype landau sequences derive realfun itv convex