fact: Definition cos_coeff x := [sequence (~~ odd n)%:R * (-1)^n./2 * x ^+ n / n`!%:R]_n.
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