proposition: Lemma derivable_cos x : derivable cos x 1.
proof: Proof. by apply: ex_derive; apply: is_derive_cos. Qed.
imports: mathcomp(all_ssreflect ssralg ssrint ssrnum matrix) mathcomp(interval rat) mathcomp(mathcomp_extra boolp classical_sets functions) reals ereal nsatz_realtype signed topology normedtype landau sequences derive realfun exp