Let $A = \left\{ \theta \in ( 0,2 \pi ) : \frac { 1 + 2 i \sin \theta } { 1 - i \sin \theta } \right.$ is purely imaginary $\}$ Then the sum of the elements in $A$ is (1) $4 \pi$ (2) $3 \pi$ (3) $\pi$ (4) $2 \pi$
Let $A = \left\{ \theta \in ( 0,2 \pi ) : \frac { 1 + 2 i \sin \theta } { 1 - i \sin \theta } \right.$ is purely imaginary $\}$ Then the sum of the elements in $A$ is\\
(1) $4 \pi$\\
(2) $3 \pi$\\
(3) $\pi$\\
(4) $2 \pi$