All the values of $(8 i)^{\frac{1}{3}}$ are

All the values of $(8 i)^{\frac{1}{3}}$ are
  1. $\pm(\sqrt{3}+i),-2 i$
  2. $\pm \sqrt{3}+i,-2 i$
  3. $\pm \sqrt{3}-i,-2 i$
  4. $\pm(2+i), i$

Solution

$\begin{aligned} & (8 i)^{1 / 3}=\left(-8 i^3\right)^{1 / 3}=-2 i \\ & i=e^{i \frac{\pi}{2}}=e^{i \frac{5 \pi}{2}} \end{aligned}$ $(8 i)^{1 / 3}=2 e^{\frac{i \pi}{6}}=2\left(\frac{\sqrt{3}}{2}+\frac{i}{2}\right)=\sqrt{3}+i$ $(8 i)^{1 / 3}=2 e^{i \frac{5 \pi}{6}}=2\left(\frac{-\sqrt{3}}{2}+\frac{i}{2}\right)=-\sqrt{3}+i$ $(8 i)^{1 / 3}= \pm \sqrt{3}+i,-2 i$.

Asked in: AP EAMCET 2024 (22 May Shift 1)

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