三十八角形
よって
6 cos  2 π 38 = x 1 + 3 x 1 + 7 x 2 − 12 − 6 ω ( x 2 − 1 ) + 3 ω 2 ( x 1 + 1 ) 3 + 3 x 1 + 7 x 2 − 12 − 6 ω 2 ( x 2 − 1 ) + 3 ω ( x 1 + 1 ) 3 {\displaystyle {\begin{aligned}6\cos {\frac {2\pi }{38}}=&x_{1}+{\sqrt[{3}]{3x_{1}+7x_{2}-12-6\omega (x_{2}-1)+3\omega ^{2}(x_{1}+1)}}+{\sqrt[{3}]{3x_{1}+7x_{2}-12-6\omega ^{2}(x_{2}-1)+3\omega (x_{1}+1)}}\\\end{aligned}}}
整理すると