proposition: Lemma derivable_tan x : cos x != 0 -> derivable tan x 1.
proof: Proof. by move=> /is_derive_tan[]. 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