>>597
sin^3(x) = (x - (x^3/6) + O(x^5))^3
より
sin^3(x) = x^3 - (x^5/2) + O(x^7)
∴ (x^3 - sin^3(x))/x^5 = 1/2 + O(x^2)
lim[x→0] (x^3 - sin^3(x))/x^5 = 1/2