Question

F(x) = 3 cos^2 4x
tentukan nilai f ' ( phi/4)

Pakai cara yaa^^9

Answer 1

F(x) = 3Cos²4x = 3(Cos4x)²
f'(x) = 3(2)(4)(Cos4x)(-Sin4x)
       = -12(2Sin4xC0s4x)
       = -12Sin2(4x)
       = -12Sin8x
f ' (π/4) = -12Sin8(π/4)
             = -12Sin2π
             = -12(0)
             = 0