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(cos x - i sin x)^n equals which expression for integer n?
Acos nx - i sin nx
Bcos nx + i sin nx
C-cos nx + i sin nx
Dcos x^n - i sin x^n
Answer & Solution
Correct answer: A. cos nx - i sin nx
Since cos x - i sin x = cos(-x) + i sin(-x), its nth power is cos(-nx) + i sin(-nx) = cos nx - i sin nx.
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