■サマーヴィルの等面四面体(その560)

  P0(1/2,(√5)/2,0,(√10)/2)

  P1(0,0,0,0)

  P2(2,0,0,0)

  P3(3/2,(√5)/2,(√10)/2,0)

  P4(1,√5,0,0)

は△4をみたす.

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【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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【2】F6 in △4

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

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

25h^2(1)

F6は

  P1P2=P2P3=P3P4=P4P5=P5P6=√6

  P1P3=P2P4=P3P5=P4P6=√10

  P1P4=P2P5=P3P6=√12

  P1P5=P2P6=√12

  P1P6=√10

4m^2+h^2=6

6m^2+4h^2=25h^2=10

4m^2+16h^2=6m^2+9h^2=12

6m^2=21h^2

4m^2=14h^2,h^2=2/5,m^2=7/5

  P0P1^2=15h^2

  P0P2^2=30^2

  P0P3^2=30h^2

  P0P4^2=25h^2

  P0P5^2=15h^2

  P1P2^2=25h^2

  P1P3^2=30h^2

  P1P4^2=30h^2

  P1P5^2=25h^2

  P2P3^2=15h^2

  P2P4^2=25h^2

  P2P5^2=30h^2

  P3P4^2=15h^2

  P3P5^2=25h^2

  P4P5^2=15h^2

となって,√6:√10:√12となった.

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【3】G7 in △4

G7は

  P2P3=P3P4=P4P5=P5P6=P6P7=√7

  P2P4=P3P5=P4P6=P5P7=√12

  P2P5=P3P6=P4P7=√15

  P2P6=P3P7=4

  P2P7=√15

4m^2+h^2=7

6m^2+4h^2=12

6m^2+9h^2=25h^2=15

4m^2+16h^2=16

h^2=3/5,m^2=8/5

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【4】H8 in △4

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

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

25h^2(1)

H8は

  P3P4=P4P5=P5P6=P6P7=P7P8=√8

  P3P5=P4P6=P5P7=P6P8=√14

  P3P6=P4P7=P5P8=√18

  P3P7=P4P8=√20

  P3P8=√20

4m^2+h^2=8

6m^2+4h^2=14

6m^2+9h^2=18

4m^2+16h^2=25h^2=20

h^2=4/5,m^2=9/5

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