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For x in [0, 2π), cos x = 1/2 holds at which pair of angles?
Aπ/3 and 2π/3
Bπ/6 and 11π/6
C2π/3 and 4π/3
Dπ/3 and 5π/3
Answer & Solution
Correct answer: D. π/3 and 5π/3
Cosine is positive in the first and fourth quadrants and equals 1/2 at π/3, so the other angle is 2π minus π/3, which is 5π/3.
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