Define Transcendental functions on arbitrary fields. These functions are defined for only a few (in most cases only one) arguments, that's why we discourage making these types instances of C. But instances of C can be useful when working with power series. If you intend to work with power series with Rational coefficients, you might consider using MathObj.PowerSeries.T (Number.PartiallyTranscendental.T Rational) instead of MathObj.PowerSeries.T Rational.