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Verified answer
Sin (x + 210°) + sin (x - 210°) = ½√3untuk sin (x + 210)
= (sinx cos (210) + cos x sin 210)
= (-½√3 sin x - ½ cos x)
untuk sin (x - 210)°
= sin x cos 210 - cos x sin 210
= -½√3 sin x - (-½) cos x
= -½√3 sin x + ½ cos x
sin (x + 210) + sin (x - 210)
= (-½√3 sin x - ½ cos x) + (-½√3 sin x + ½ cos x)
= -√3 sin x
sin (x + 210) + sin (x - 210) = ½√3
-√3 sin x = ½√3
sin x = ½√3 / (-√3)
sin x = -½
x = 210°, 330°
atau
x = 7/6π, 11/6π