  The Wigner d function, which is the essential part of an irreducible
representation of SU(2) and SO(3) parameterized with Euler angles, has been
know to suffer from a serious numerical errors at high spins, if it is
calculated by means of the Wigner formula as a polynomial of cos and sin of
half of the second Euler angle. This paper shows a way to avoid this problem by
expressing the d functions as the Fourier series of the half angle. A precise
numerical table of the coefficients of the series is obtainable from a web
site.
