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TS EAMCET · Maths · Complex Number

If \(\left(\frac{\sqrt{3}+i}{\sqrt{3}-i}\right)^4+\left(\frac{\sqrt{3}-i}{\sqrt{3}+i}\right)^4=r\) cis \(\theta\), then one of the values of \(\sqrt{\mathrm{r} \operatorname{cis} \theta}\) is

  1. A \(\operatorname{cis}\left(\frac{3 \pi}{4}\right)\)
  2. B \(\operatorname{cis}\left(\frac{3 \pi}{2}\right)\)
  3. C \(\operatorname{cis}\left(\frac{\pi}{3}\right)\)
  4. D \(\operatorname{cis} \pi\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\operatorname{cis}\left(\frac{3 \pi}{2}\right)\)

Step-by-step Solution

Detailed explanation

\begin{aligned} & \text { }\left(\frac{\sqrt{3}+i}{\sqrt{3}-i}\right)^4+\left(\frac{\sqrt{3}-i}{\sqrt{3}+i}\right)^4 \\ & =\left(\frac{\sqrt{3}+i}{\sqrt{3}-i} \times \frac{\sqrt{3}+i}{\sqrt{3}+i}\right)^4+\left(\frac{\sqrt{3}-i}{\sqrt{3}+i} \times…