Answer
negative; III; $60^{\circ}$; $-\frac{\sqrt 3}{2}$
Work Step by Step
As $\theta=240^{\circ}$ is in between $180^{\circ}$ and $270^{\circ}$, it is in the third quadrant. In the third quadrant, all trigonometric functions are negative except tangent and cotangent functions. Therefore, the value of $\sin240^{\circ}$ is negative.
For third quadrant, Reference angle $\theta'=\theta-180^{\circ}=240^{\circ}-180^{\circ}=60^{\circ}$
$\sin240^{\circ}=-\sin\theta'=-\sin60^{\circ}=-\frac{\sqrt 3}{2}$
