proposition: Lemma cospi : cos pi = - 1.
proof: Proof. by rewrite /pi mulr2n cosD -pihalfE sin_pihalf mulr1 cos_pihalf mulr0 add0r. 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