18/08/06 17:10:06.18 840AtD1X.net
cos(11θ) + 1
= (cosθ+1) {cos(11θ/2) / cos(θ/2)}^2
= (cosθ+1) {[sin(6θ) - sin(5θ)] / sinθ}^2,
より
T_11(x) + 1 = (x+1) {U_5(x) - U_4(x)}^2
= (x+1) (32x^5 -16x^4 -32x^3 +12x^2 +6x -1)^2,
第二種チェビシェフ多項式
U_4(x) = 16x^4 -12x^2 +1,
U_5(x) = 32x^5 -32x^3 +6x,