Answer
0
Work Step by Step
We can find the sine of coterminal angle that belongs to [$0^{\circ}$,$360^{\circ}$) for convenience.
$\sin(-900^{\circ})= $
$\sin(-900^{\circ}+3\cdot360^{\circ})=\sin 180^{\circ}$
The terminal side of $180^{\circ}$ angle passes through (-1,0). So $x=-1,y=0$ and $r=1$.
$\sin 180^{\circ}=\frac{y}{r}=\frac{0}{1}=0$
