回復 16# studentJ 的帖子
非選第 2 題
設\(x^5-1=0\)的5個根在複數平面上對應到\(A,B,C,D,E\)五個點,試求\(\overline{AB}\times \overline{AC}\times \overline{AD}\times \overline{AE}\)。
[解答]
\(\begin{align}
& \overline{AB}\times \overline{AC}\times \overline{AD}\times \overline{AE}=\left| 1-\omega \right|\left| 1-{{\omega }^{2}} \right|\left| 1-{{\omega }^{3}} \right|\left| 1-{{\omega }^{4}} \right| \\
& \omega =\cos \frac{2\pi }{5}+i\sin \frac{2\pi }{5} \\
\end{align}\)