(i)$$\frac{1-{\cos }^4\theta }{1-{\mathrm{sen}}^4\theta }\cdot \frac{1+{\mathrm{cotg}}^2\theta }{1+{\mathrm{tg}}^2\theta }=\frac{2}{3}$$

(ii) $\theta \in [0,2\pi ]$ radianos.