fact: Definition cos_coeff' x (n : nat) := (-1)^n * x ^+ n.*2 / n.*2`!%:R.
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