五十二角形
cos  ( 2 π / 52 ) {\displaystyle \cos(2\pi /52)} を平方根と立方根で表すと
cos  2 π 52 = 1 6 13 − 3 13 2 + 1 6 13 + 3 13 2 − 5 13 26 + i 3 39 26 3 + 1 6 13 + 3 13 2 − 5 13 26 − i 3 39 26 3 {\displaystyle \cos {\frac {2\pi }{52}}={\frac {1}{6}}{\sqrt {\frac {13-3{\sqrt {13}}}{2}}}+{\frac {1}{6}}{\sqrt {\frac {13+3{\sqrt {13}}}{2}}}{\sqrt[{3}]{{\frac {-5{\sqrt {13}}}{26}}+i{\frac {3{\sqrt {39}}}{26}}}}+{\frac {1}{6}}{\sqrt {\frac {13+3{\sqrt {13}}}{2}}}{\sqrt[{3}]{{\frac {-5{\sqrt {13}}}{26}}-i{\frac {3{\sqrt {39}}}{26}}}}}