(a)[2]
The diagram gives part of the graph of $y = a + b \sin x$. Find the values of the constants $a$ and $b$.
(b(i))[3]
Show that $(\sin \theta + 2\cos \theta)(1 + \sin \theta - \cos \theta) = \sin \theta (1 + \cos \theta)$ can be rewritten as $3\cos^2 \theta - 2\cos \theta - 1 = 0$.
(b(ii))[4]
Hence, solve the equation $(\sin \theta + 2\cos \theta)(1 + \sin \theta - \cos \theta) = \sin \theta (1 + \cos \theta)$ for $-180^\circ \leq \theta \leq 180^\circ$.