What are all the exact solutions of cosine x is equal to negative the fraction with numerator square root of 3 and denominator 2 on the interval pi is less than or equal to x comma x is less than or equal to 2 pi ? Give your answer in radians.

The reference angle for cosine with magnitude √3/2 is π/6. Cosine is negative in Quadrants II and III, giving 5π/6 and 7π/6 on one full turn. Only 7π/6 lies in the interval from π to 2π, so the exact solution is 7π/6, choice A.

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