If z = cos(π/7) + i sin(π/7), then z⁷ equals:
Ai
B-1
C1
D-i
Answer & Solution
Correct answer: B. -1
By DeMoivre: z⁷ = (cos π/7 + i sin π/7)⁷ = cos(π) + i sin(π) = -1 + 0i = -1.
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