proposition: Lemma pihalfE : pi / 2 = get [set x | 0 <= x <= 2 /\ cos x = 0].
proof: Proof. by rewrite /pi -[_ *+ 2]mulr_natr -mulrA divff ?mulr1. 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