■等面単体の体積(その390)

 ここからは,nの展開図の断面は,n−1次元等面単体のファセットに成っていることを確かめてみたい.

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  P1(0,0,0)

  P2(1,√2,0)

  P3(2,0,0)

  P1P2=P2P3=√3

  P1P3=2

を満たす.

  P1(0,0,0)

  P2(m,m√2,0)

  P3(2m,0,0)

  P0(0,0,0,0)

  P1(0,0,0,3h)

  P2(m,m√2,0,2h)

  P3(2m,0,0,h)

とおくと

  P0P1^2=9h^2

  P0P2^2=3m^2+4h^2

  P0P3^2=4m^2+4h^2

  P1P2^2=3m^2+h^2

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

  P2P3^2=3m^2+h^2

3m^2+h^2(2)<3m^2+4h^2(1)<4m^2+4h^2(2)

9h^2(1)

  P0(0,0,0,0)

  P1(0,0,0,3h)

  P2(m,m√2,0,h)

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

とおくと

  P0P1^2=9h^2

  P0P2^2=3m^2+h^2

  P0P3^2=4m^2+4h^2

  P1P2^2=3m^2+4h^2

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

  P2P3^2=3m^2+h^2

3m^2+h^2(2)<3m^2+4h^2(1)

4m^2+h^2(1)<4m^2+4h^2(1)

9h^2(1)

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 n=4の展開図は

  P1P2=P2P3=P3P4=2

  P1P3=P2P4=√6

  P1P4=√6

であるから,どちらもNG.hの与え方に問題があるのだろうか?

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