proposition: Lemma atan_ltpi2 x : atan x < pi / 2.
proof: Proof. by case: (atan_def x) => [] /andP[]. 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