■サマーヴィルの等面四面体(その630)

【1】△5 in △4

  P0(m/2,m√5/2,0,m√10/2,h)

  P1(0,0,0,0,0)

  P2(0,0,0,0,5h)

  P3(2m,0,0,0,4h)

  P4(3m/2,m√5/2,m√10/2,0,3h)

  P5(m,m√5,0,0,2h)

としてみる.

  P0P1^2=4m^2+h^2

  P0P2^2=4m^2+16h^2

  P0P3^2=6m^2+9h^2

  P0P4^2=6m^2+4h^2

  P0P5^2=4m^2+h^2

  P1P2^2=25h^2

  P1P3^2=4m^2+16h^2

  P1P4^2=6m^2+9h^2

  P1P5^2=6m^2+4h^2

  P2P3^2=4m^2+h^2

  P2P4^2=6m^2+4h^2

  P2P5^2=6m^2+9h^2

  P3P4^2=4m^2+h^2

  P3P5^2=6m^2+4h^2

  P4P5^2=4m^2+h^2

4m^2+h^2(5)<4m^2+16h^2(2)

6m^2+4h^2(4)<6m^2+9h^2(3)

25h^2(1)

  25h^2=4m^2+h^2=5,h^2=1/5,m^2=6h^2=6/5

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a^2=4m^2+h^2(5)

b^2=6m^2+4h^2(4)

c^2=6m^2+9h^2(3)

d^2=4m^2+16h^2(2)

e^2=25h^2(1)

h^2を消去すると

a^2−4m^2=(b^2−6m^2)/4=(c^2−6m^2)/9=(d^2−4m^2)/16=e^2/25

b^2,c^2,d^2,e^2をa^2,m^2で表すと

b^2=4a^2−10m^2

c^2=9a^2−30m^2

d^2=16a^2−60m^2

e^2=25a^2−100m^2

10b^2=40a^2−100m^2

−10c^2=−90a^2+300m^2

5d^2=80a^2−300m^2

−e^2=−25a^2+100m^2

10b^2−10c^2+5d^2−e^2=5a^2  (OK)

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[まとめ] (m^2,h^2)システムからも同じ結果を導き出すことはできたが,やはり実験式という側面は否めない.

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