■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.
===================================
【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
===================================
【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.
===================================
【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
===================================
【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
===================================