>>407 (続き)

a = 2-√2 だから
　X = Y + {(2-√2)/3!}Y^3 + {(58-39√2)/5!}Y^5 + {(5266-3697√2)/7!}Y^7 + {(956274-675503√2)/9!}Y^9 + ････
ここに
　X = x + (3π/4),
　Y = (√2 -1){cos(t) -1 +(3π/4)},