For any integer k,let alpha_k = cos left(frac | vedclass

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(D) Given $\alpha_k = e^{i \frac{k \pi}{7}}$.Then $|\alpha_{k+1} - \alpha_k| = |e^{i \frac{(k+1) \pi}{7}} - e^{i \frac{k \pi}{7}}| = |e^{i \frac{k \pi

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$4$

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(D) Given $\alpha_k = e^{i \frac{k \pi}{7}}$.Then $|\alpha_{k+1} - \alpha_k| = |e^{i \frac{(k+1) \pi}{7}} - e^{i \frac{k \pi}{7}}| = |e^{i \frac{k \pi}{7}}| |e^{i \frac{\pi}{7}} - 1| = |e^{i \frac{\pi}{7}} - 1|$.The numerator is $\sum_{k=1}^{12} |e^{i \frac{\pi}{7}} - 1| = 12 |e^{i \frac{\pi}{7}} - 1|$.The denominator is $\sum_{k=1}^3 |e^{i \frac{(4k-1) \pi}{7}} - e^{i \frac{(4k-2) \pi}{7}}| = \sum_{k=1}^3 |e^{i \frac{(4k-2) \pi}{7}}| |e^{i \frac{\pi}{7}} - 1| = 3 |e^{i \frac{\pi}{7}} - 1|$.Thus,the ratio is $\frac{12 |e^{i \frac{\pi}{7}} - 1|}{3 |e^{i \frac{\pi}{7}} - 1|} = \frac{12}{3} = 4$.

For any integer $k$,let $\alpha_k = \cos \left(\frac{k \pi}{7}\right) + i \sin \left(\frac{k \pi}{7}\right)$,where $i = \sqrt{-1}$. The value of the expression $\frac{\sum_{k=1}^{12} |\alpha_{k+1} - \alpha_k|}{\sum_{k=1}^3 |\alpha_{4k-1} - \alpha_{4k-2}|}$ is

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