$\sin \left(-{2490}^{\circ }\right)=\sin \left({360}^{\circ }\cdot 7-{2490}^{\circ }\right)=\sin \left({2520}^{\circ }-{2490}^{\circ }\right)=\sin {30}^{\circ }=\frac{1}{2}$ $\sin \left(-{2490}^{\circ }\right)=\sin \left({360}^{\circ }\cdot 7-{2490}^{\circ }\right)=\sin \left({2520}^{\circ }-{2490}^{\circ }\right)=\sin {30}^{\circ }=\frac{1}{2}$  

 

$\text{Odpowiedzˊ C.}$