If 0<θ, φ<(π)/2, x=Σ_n =0^∞ cos^2 n θ, y=Σ_n =0^∞ sin^2 n φ and z=Σ_n =0^∞ cos^2 n θ · sin^2 n φ then:

If $\displaystyle 0<\theta, \phi<\frac{\pi}{2}, x=\sum_{\mathrm{n}=0}^{\infty} \cos ^{2 \mathrm{n}} \theta, y=\sum_{\mathrm{n}=0}^{\infty} \sin ^{2 \mathrm{n}} \phi$ and $\displaystyle z=\sum_{\mathrm{n}=0}^{\infty} \cos ^{2 \mathrm{n}} \theta \cdot \sin ^{2 \mathrm{n}} \phi$ then :