proposition: Lemma cos_coeff_2_2 : cos_coeff 2 2%N = - 2%:R :> R.
proof: Proof. by rewrite /cos_coeff /= mul1r expr1z mulN1r expr2 mulNr -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