If $\omega$ is a complex cube root of unity, then $\sin \left\{\left(\omega^{10}+\omega^{23}\right)…

If $\omega$ is a complex cube root of unity, then $\sin \left\{\left(\omega^{10}+\omega^{23}\right) \pi-\frac{\pi}{4}\right\}=$
  1. $\frac{1}{\sqrt{2}}$
  2. $\frac{1}{2}$
  3. 1
  4. $\frac{\sqrt{3}}{2}$

Solution

It is given that $w$ is a complex cube root of unity, so $w^3=1$ and $w^2+w+1=0$. So, $\sin \left\{\left(w^{10}+w^{23}\right) \pi-\frac{\pi}{4}\right\}$ $ \begin{aligned} & =\sin \left\{\left(w+w^2\right) \pi-\frac{\pi}{4}\right\} \\ & =-\sin \left(\pi+\frac{\pi}{4}\right)=\sin \frac{\pi}{4}=\frac{1}{\sqrt{2}} \end{aligned} $ Hence, option (1) is correct

Asked in: AP EAMCET 2020 (22 Sep Shift 1)

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