Tolong dijawab. Turunan pertama fungsi f(x)= 4cos²(x- π)

f(x) = 4cos^2(x- π)
f(x) = 4 { cos(x -π) }^2
f'(x) = 4.2 { cos(x-π) }^(2-1).-sin(x-π)
f'(x) = -8 cos(x-π) sin(x-π)
= -4 { 2cos(x-π) sin(x-π)
= -4 sin {2(x-π) }