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For z = cos θ + i sin θ, z^n added to its reciprocal power gives what?
A2 cos nθ
B2i sin nθ
C2 sin nθ
Dcos nθ
Answer & Solution
Correct answer: A. 2 cos nθ
z^n = cos nθ + i sin nθ and z^−n = cos nθ − i sin nθ, so the imaginary parts cancel to leave 2 cos nθ.
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