If z=eithetaz = e^{i\\theta}z=eitheta, then costheta\\cos\\thetacostheta in terms of zzz is:
z−barzz - \\bar{z}z−barz
(z+1/z)/2(z + 1/z) / 2(z+1/z)/2
(z−1/z)/2i(z - 1/z) / 2i(z−1/z)/2i
z+barzz + \\bar{z}z+barz