MCQ
The value of ${( - i)^{1/3}}$ is
  • A
    $\frac{{1 + \sqrt 3 i}}{2}$
  • B
    $\frac{{\sqrt 3  - i}}{2}$
  • C
    $\frac{{ - \sqrt 3 - i}}{2}$
  • $(b) $ and $ (c)$  both

Answer

Correct option: D.
$(b) $ and $ (c)$  both
d
(d) Since $\frac{{ - \sqrt 3 - i}}{2} = - \left( {\cos \frac{\pi }{6} + i\sin \frac{\pi }{6}} \right)$
==> ${\left( {\frac{{ - \sqrt 3 - i}}{2}} \right)^3} = - {\left( {\cos \frac{\pi }{6} + i\sin \frac{\pi }{6}} \right)^3} = - i$
and $\frac{{\sqrt 3 - i}}{2} = \cos \frac{\pi }{6} - i\sin \frac{\pi }{6}$
and ${\left( {\frac{{\sqrt 3 - i}}{2}} \right)^3} = \cos \frac{\pi }{2} - i\sin \frac{\pi }{2} = - i$.
Hence the result.

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