proposition: Lemma continuous_tan x : cos x != 0 -> {for x, continuous tan}.
proof: Proof. move=> cxNZ. apply: continuousM; first exact: continuous_sin. exact/(continuousV cxNZ)/continuous_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