$\sin150^{\circ}=\sin(180^{\circ}-30^{\circ})=\sin30^{\circ}=\dfrac{1}{2}\\ \cos150^{\circ}=\cos(180^{\circ}-30^{\circ})=-\cos30^{\circ}=-\dfrac{\sqrt{3}}{2}\\ \tan150^{\circ}=\tan(180^{\circ}-30^{\circ})=-\tan30^{\circ}=-\dfrac{\sqrt{3}}{3}=\dfrac{-1}{\sqrt{3}}$ Chọn C
