(i)[3]
Express $0.5\cos\theta - 1.2\sin\theta$ in the form $R\cos(\theta + \alpha)$, where $R > 0$ and $0^{\circ} < \alpha < 90^{\circ}$, and give the value of $\alpha$ correct to $2$ decimal places.
(ii)[4]
Hence solve the equation $0.5\cos\theta - 1.2\sin\theta = 0.8$ in the interval $0^{\circ} < \theta < 360^{\circ}$.
(iii)[3]
Find the greatest and least possible values of $(3 - \cos\theta + 2.4\sin\theta)^2$ as $\theta$ changes.