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(cos θ + i sin θ)³ equals which of the following?
Acos θ + i sin θ
B3 cos θ + 3i sin θ
Ccos θ³ + i sin θ³
Dcos 3θ + i sin 3θ
Answer & Solution
Correct answer: D. cos 3θ + i sin 3θ
Putting n = 3 in the theorem triples the angle to give cos 3θ + i sin 3θ.
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