■単純リー環を使った面数数え上げ(その158)
億劫がらずに3次元5回回転対称図形を扱うことにした.
a1=1,a2=√(1/3),a3=τ^2/√3
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[1]{3,5}(010)
1−y1=(y2−y3)/√(3+3/τ^4)=0→y1=1(辺の二等分点),y2=y3=0
(y1−y2)/√4=L,L=1/2
c0=a1^2(1−y1)+a2^2(1−y2)+a3^2(1−y3)=1/3+τ^4/3
d0=(1+1/3+τ^4/3)^1/2=(4/3+τ^4/3)^1/2
h0=(1+τ^4)/3・√{3/(4+τ^4)}
c2=a3^2(1−y3)=τ^4/3
‖d2‖=(a3^2)^1/2=τ^2/√3
h2=|c2|/‖d2‖=τ^2/√3
また,
→V2=1/2・tan54°×5/2={(5+2√5)/5}^1/2・5/4(正五角形の面積)
→Λ2=√3/4(正三角形の面積)
3V・2L=(N0・V2・h0+N2・Λ2・h2)
={12・5{(5+2√5)/5}^1/2/4・(1+τ^4)/√{3(4+τ^4)}+20・√3/4・τ^2/√3}
=τ√5・(1+τ^4)+5τ^2
V=τ√5・(1+τ^4)/3+5τ^2/3
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[2]{3,5}(011)
1−y1=0
(y1−y2)/√4=(y2−y3)/√(3+3/τ^4)=L
√(3+3/τ^4)=3/τ→y1=1,y2=3/(2τ+3)=3(4−√5)/11,y3=0,L=(3√5−1)/22
c0=a1^2(1−y1)+a2^2(1−y2)+a3^2(1−y3)=(3√5−1)/33+τ^4/3
d0=(1+1/3+τ^4/3)^1/2=(4/3+τ^4/3)^1/2
h0=((3√5−1)/33+τ^4/3)・√{3/(4+τ^4)}
c2=a3^2(1−y3)=τ^4/3
‖d2‖=(a3^2)^1/2=τ^2/√3
h2=|c2|/‖d2‖=τ^2/√3
また,
→V2=1/2・tan72°×10/2={(5+2√5)}^1/2・10/4(正十角形の面積)
→Λ2=√3/4(正三角形の面積)
3V・2L=(N0・V2・h0+N2・Λ2・h2)
={12・10{(5+2√5)}^1/2/4・((3√5−1)/33+τ^4/3)・√{3/(4+τ^4)}+20・√3/4・τ^2/√3}
=30τ((3√5−1)/33+τ^4/3)+5τ^2
=10τ(3√5−1)/11+10τ^5+5τ^2
V={10τ(3√5−1)/11+10τ^5+5τ^2}/6L
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