■基本単体の二面角(その273)
有限群
αn:aj=(2/j(j+1))^1/2
βn:bj=(2/j(j+1))^1/2,bn=√(2/n)
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[1]An
正単体において,R=nrはよく知られている.
(R/ρ)^2=n^2
R^2=1+1/3+・・・+2/n(n−1)+an^2=2−2/n+an^2
ρ^2=an^2
(2−2/n+an^2)/an^2=n^2→an^2=2/n(n+1) (OK)
−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
[2]BCn
R=r√nより
(R/ρ)^2=n
R^2=1+1/3+・・・+2/n(n−1)+an^2=2−2/n+an^2
ρ^2=an^2
(2−2/n+an^2)/an^2=n→an^2=2/n (OK)
R^2=1+1+・・・+1+an^2=(n−1)+an^2
ρ^2=an^2
(n−1+an^2)/an^2=n→an^2=1 (OK)
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