Densities for the angle Θ = uX(mod 2π) and the cosine $Y = \cos(uX)$ can be expressed, through Fourier methods, in terms of the characteristic function of X. Thus ...
Kövari and Pommerenke [19], and Elliott [8], have shown that the truncated Faber series gives a polynomial approximation which (for practical values of the degree of the polynomial) is very close to ...