proposition: Lemma exprn_even_lt0 n x : ~~ odd n -> (x ^+ n < 0) = false.
proof: Proof. by move=> even_n; rewrite real_exprn_even_lt0 ?num_real. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)