Principal solutions of a basic trig equation

1. A.
   $\dfrac{2\pi}{3}, \dfrac{4\pi}{3}$
2. B.
   $\dfrac{4\pi}{3}, \dfrac{5\pi}{3}$
3. C.
   $\dfrac{5\pi}{6}, \dfrac{7\pi}{6}$
4. D.
   $\dfrac{7\pi}{6}, \dfrac{11\pi}{6}$

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1. A.
   $\frac{- \pi}{3},\frac{2\pi}{3}$
2. B.
   $\frac{2\pi}{3},\frac{5\pi}{3}$
3. C.
   $\frac{2\pi}{3},\frac{4\pi}{3}$
4. D.
   $\frac{2\pi}{3},\frac{7\pi}{3}$

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1. A.
   $\dfrac{\pi}{6}, \dfrac{5\pi}{6}$
2. B.
   $\dfrac{5\pi}{6}, \dfrac{7\pi}{6}$
3. C.
   $\dfrac{7\pi}{6}, \dfrac{11\pi}{6}$
4. D.
   $\dfrac{\pi}{6}, \dfrac{11\pi}{6}$

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