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Two angles in [0, 2π] satisfy cos x = −1/2. They are
Aπ/3 and 2π/3
Bπ/6 and 5π/6
C2π/3 and 4π/3
D5π/6 and 7π/6
Answer & Solution
Correct answer: C. 2π/3 and 4π/3
Cosine is negative in quadrants two and three with reference angle π/3, giving 2π/3 and 4π/3.
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