Bantu plisss.. soal turunan trigonometri

Aturan berantai : y= f(x)^n
y'=n . f(x)^n-1 . f'(x)

f(x) = sin x + cos x
n = 2

y' = 2 (sin x+cos x)^1 (cos x + (-sin x))
y' = 2 ( cos x+sin x)(cos x-sin x)
= 2(cos^2 x-sin^2 x)
= 2 cos 2x
= 2 ( 2 cos^2 x - 1)
= 4 cos^2 x - 2