(i)[3]
Show that the equation $\dfrac{2\sin\theta + \cos\theta}{\sin\theta + \cos\theta} = 2\tan\theta$ can be rearranged into the form $\cos^2\theta = 2\sin^2\theta$.
(ii)[3]
Hence solve the equation $\dfrac{2\sin\theta + \cos\theta}{\sin\theta + \cos\theta} = 2\tan\theta$ when $0^\circ < \theta < 180^\circ$.