jika f(x) = (2x+1) cos(2x+phi) dan f'(x) adalah turunan pertama dari f(x). Nilai f'(phi/2) adalah

Turunan

f(x)= (2x+1) . cos(2x +π)
y = u v
u = 2x +1 --> u' = 2
v = cos(2x +π) --> v' = - 2 sin (2x + π)

y'= u'v + uv'

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

x = π/2
y' = 2 cos(π+π) + (-2π-2) sin(π+π)
y' = 2 cos 2π + (-2π-2) sin 2π
y' = 2(1) + (-2π-2)(0)
y' = 2