- 638 名前：ﾛには、入射角 = 反射角 となる。
反射面の傾きmは
2m/(1-mm) = (b[n-1]+2b[n]+b[n+1])/{1 - (b[n-1]+b[n])(b[n]+b[n+1])},
点P(n)での接線の傾きは m = 2b[n],
b[n] の漸化式は
4b[n](b[n]^2 - b[n-1]b[n+1] - 1) = b[n+1] - 6b[n] + b[n-1],
(b[n+1]^2 - 6b[n+1]b[n] + b[n]^2) - (b[n]^2 - 6b[n]b[n-1] + b[n-1]^2)
= (b[n+1] - b[n-1])(b[n+1] - 6b[n] + b[n-1]),
なので
b[n+1] - 6b[n] + b[n-1] = 0,
b[n+1]^2 - 6b[n+1]b[n] + b[n]^2 = 1,
b[n]^2 - b[n+1]b[n-1] = 1,
を示せばよい… [] - [ここ壊れてます]
