proposition: Lemma tan_pihalf : tan (pi / 2) = 0.
proof: Proof. by rewrite /tan cos_pihalf invr0 mulr0. 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