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Find the two angles in [0, 2π] whose cosine is the negative of one half.
Aπ/6 and 5π/6
B5π/6 and 7π/6
Cπ/3 and 5π/3
D2π/3 and 4π/3
Answer & Solution
Correct answer: D. 2π/3 and 4π/3
Cosine is negative in the second and third quadrants, giving π - π/3 = 2π/3 and π + π/3 = 4π/3.
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