A) \[cis\frac{\pi }{12}\]
B) \[cis\frac{\pi }{2}\]
C) \[cis\frac{\pi }{6}\]
D) \[cis\frac{\pi }{3}\]
Correct Answer: A
Solution :
From the given answer choices we see that \[{{\left( cis\frac{\pi }{12} \right)}^{4}}=cis\frac{4\pi }{12}\] \[=cis\frac{\pi }{3}\] \[\Rightarrow \] \[\cos \frac{\pi }{3}+i\sin \frac{\pi }{3}\] \[=\frac{1}{2}+i\frac{\sqrt{3}}{2}\]
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