■DE群多面体の面数公式(その801)

[1]E5=121

 頂点間距離が2のとき,半径は√(5/2)

 R^2=1+1/3+1/6+1/10+a5^2=5/2

=1+1/3+1/6+2/4+b5^2

 1+1/3+1/6=(6+2+1)/6=3/2

 R^2=3/2+1/2+b5^2=3/2+1/10+a5^2=5/2

 a5^2=(25−15−1)/10=9/10

 b5^2=(25−15−5)/10=1/2

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[2]E4=t1α4

 頂点間距離が2のとき,半径は√(12/5)

 R^2=1+1/3+1/6+a4^2=12/5

=1+1/3+2/3+b4^2

 1+1/3=(3+1)/3=4/3

 R^2=4/3+2/3+b4^2=4/3+1/6+a4^2=12/5

 a4^2=(72−40−5)/30=9/10

 b4^2=(72−40−20)/30=4/10

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[3]E3=正三角柱

 頂点間距離が2のとき,半径は√(7/3)

 R^2=1+1/3+a3^2=7/3

=1+2/2+b3^2

 R^2=2+b3^2=4/3+a3^2=7/3

 a3^2=1

 b4^2=1/3

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