Question

26. Let \( \omega=\cos 3^{\circ}+i \sin 3^{\circ} \) then \( \sum_{r=1}^{10} \operatorname{Re}\left(\omega^{2 r-1}\right) \) equals (1) \( \frac{1}{\sin 3^{\circ}} \) (2) \( \frac{2}{\cos 3^{\circ}} \) (3) \( \frac{\sqrt{3}}{4 \sin 3^{\circ}} \) (4) \( \frac{\sqrt{3}}{2 \cos 3^{\circ}} \)

Answer 1

Hope you understand the method.

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