1.
If 0<θ<π20 < \theta < \dfrac{\pi}{2}, x=n=0cos2nθx = \sum\limits_{n=0}^{\infty} \cos^{2n} \theta, y=n=0sin2nθy = \sum\limits_{n=0}^{\infty} \sin^{2n} \theta and z=n=0cos2nθsin2nθz = \sum\limits_{n=0}^{\infty} \cos^{2n} \theta \cdot \sin^{2n} \theta, then