Calculus
posted by Sarah .
Differentiate each function
a) y = Cos³ x
b) y = Sin(x³)
c) y = Sin²xCos3x

a)
let z = cos x then dz/dx = sin x
y = z^3
y' = 3 z^2 dz/dx
y' = 3 cos^2 x (sin x)
= 3 sin x cos^2 x 
b)
let z = x^3 then dz/dx = 3 x^2
y = sin z
y' = cos z dz/dx
= cos(x^3) (3 x^2)
= 3 x^2 cos x^3 
c)y' = sin^2 x (3sin 3x)+ cos 3x (2 sin x cos x
= 3sin 3x sin^2 x + 2 cos 3x sin x cos x