三十八角形
両辺の立方根を取ると
2 cos  2 π 38 + ω ⋅ 2 cos  22 π 38 + ω 2 ⋅ 2 cos  14 π 38 = 3 x 1 + 7 x 2 − 12 − 6 ω ( x 2 − 1 ) + 3 ω 2 ( x 1 + 1 ) 3 2 cos  2 π 38 + ω 2 ⋅ 2 cos  22 π 38 + ω ⋅ 2 cos  14 π 38 = 3 x 1 + 7 x 2 − 12 − 6 ω 2 ( x 2 − 1 ) + 3 ω ( x 1 + 1 ) 3 {\displaystyle {\begin{aligned}2\cos {\frac {2\pi }{38}}+\omega \cdot 2\cos {\frac {22\pi }{38}}+\omega ^{2}\cdot 2\cos {\frac {14\pi }{38}}=&{\sqrt[{3}]{3x_{1}+7x_{2}-12-6\omega (x_{2}-1)+3\omega ^{2}(x_{1}+1)}}\\2\cos {\frac {2\pi }{38}}+\omega ^{2}\cdot 2\cos {\frac {22\pi }{38}}+\omega \cdot 2\cos {\frac {14\pi }{38}}=&{\sqrt[{3}]{3x_{1}+7x_{2}-12-6\omega ^{2}(x_{2}-1)+3\omega (x_{1}+1)}}\\\end{aligned}}}