y = cos²x d²y/dx² = .....

berikut penyelesaiannya.....

y = cos²x
misal u=cos x
dy/dx = dy/du . du/dx
=d(u²)/du . d(cos x)/dx
=2 u . sin x
dy/dx = 2 cos x sin x = sin 2x

d²y / dx² = d/dx (dy/dx)
=d/dx (sin 2x)
misal u = 2x
d/dx (sin 2x) = d/du (sin u) . d/dx (2x)
= cos u . 2
= 2 cos 2x ...