proposition: Lemma split_norm_add (x y e : F) : `|x| < e / 2%:R -> `|y| < e / 2%:R -> `|x + y| < e.
proof: Proof. by move=> hx hy; rewrite (le_lt_trans (ler_norm_add _ _)) // splitD. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice fintype) mathcomp(bigop order ssralg ssrnum ssrint rat poly polydiv polyorder) mathcomp(perm matrix mxpoly polyXY binomial bigenough)