lim x menuju 0 cos^2x.sinx-sin^3x/7x

jika gini 
lim x→0 (cos²x sinx - sin³x)/(7x)
= lim x→0 ((1 - sin²x)sinx(1 - sin²x))/(7x)
= lim x→0 sinx(1 - sin²x)²/(7x)
= lim x→0 sinx (cos²x)²/(7x)
= lim x→0 (sinx / x)(cos^4(x) / 7)
= (1)(cos^4(0) / 7)
= 1/7