[tex]\it \dfrac{5\pi}{6} =\dfrac{5\cdot 180^o}{6} = 5\cdot30^o =150^o
\\\;\\ \\\;\\
sin 150^o=sin(180^o-150^o) = sin30^o =\dfrac{1}{2}[/tex]
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[tex]\it sin\dfrac{5\pi}{6} = sin\dfrac{6\pi-\pi}{6} = sin\left(\pi-\dfrac{\pi}{6}\right) =sin\dfrac{\pi}{6} = \dfrac{1}{2}[/tex]
