(a(i))[3]
Express $\dfrac{\tan^2 \theta - 1}{\tan^2 \theta + 1}$ as $a\sin^2 \theta + b$, with $a$ and $b$ as the constants to determine.
(a(ii))[2]
Solve $\dfrac{\tan^2 \theta - 1}{\tan^2 \theta + 1} = \dfrac{1}{4}$ for $-90^\circ \leq \theta \leq 0^\circ$, showing all necessary working and, if helpful, using the earlier result.
(b(i))[2]
Find the $x$-coordinate for $A$.
(b(ii))[2]
Find the $y$-coordinate for $B$.