六十三角形
cos  2 π 63 = ω σ 7 5 3 + ω 2 σ 7 2 3 2 {\displaystyle \cos {\frac {2\pi }{63}}={\frac {{\sqrt[{3}]{\omega \sigma _{7}^{5}}}+{\sqrt[{3}]{\omega ^{2}\sigma _{7}^{2}}}}{2}}}
ここで、 ω = e 2 π 3 i , σ 7 = e 2 π 7 i . {\displaystyle \omega =e^{{\frac {2\pi }{3}}i},\sigma _{7}=e^{{\frac {2\pi }{7}}i}.}