五十六角形
x 1 = 2 cos  2 π 56 + 2 cos  50 π 56 + 2 cos  18 π 56 = 14 − 2 2 x 2 = 2 cos  10 π 56 + 2 cos  26 π 56 + 2 cos  22 π 56 = 14 + 2 2 x 3 = 2 cos  54 π 56 + 2 cos  6 π 56 + 2 cos  38 π 56 = − 14 + 2 2 x 4 = 2 cos  46 π 56 + 2 cos  30 π 56 + 2 cos  34 π 56 = − 14 − 2 2 {\displaystyle {\begin{aligned}&x_{1}=2\cos {\frac {2\pi }{56}}+2\cos {\frac {50\pi }{56}}+2\cos {\frac {18\pi }{56}}={\frac {{\sqrt {14}}-{\sqrt {2}}}{2}}\\&x_{2}=2\cos {\frac {10\pi }{56}}+2\cos {\frac {26\pi }{56}}+2\cos {\frac {22\pi }{56}}={\frac {{\sqrt {14}}+{\sqrt {2}}}{2}}\\&x_{3}=2\cos {\frac {54\pi }{56}}+2\cos {\frac {6\pi }{56}}+2\cos {\frac {38\pi }{56}}={\frac {-{\sqrt {14}}+{\sqrt {2}}}{2}}\\&x_{4}=2\cos {\frac {46\pi }{56}}+2\cos {\frac {30\pi }{56}}+2\cos {\frac {34\pi }{56}}={\frac {-{\sqrt {14}}-{\sqrt {2}}}{2}}\\\end{aligned}}}