f(x)=cos2x+x√3, x∈[0,4π]
f¹(x)= -2sin2x+√3=0, sin2x=√3/2, 2x=(-1)^n*π/3+πn, x=(-1)^n*π/6+πn/2, n∈Z
x=π/6, 4π/6, 7π/6, 10π/6 , 11π/6, 16π/6, 19π/6, 22π/6.
f(x)=cos2x+x√3, x∈[0,4π]
f¹(x)= -2sin2x+√3=0, sin2x=√3/2, 2x=(-1)^n*π/3+πn, x=(-1)^n*π/6+πn/2, n∈Z
x=π/6, 4π/6, 7π/6, 10π/6 , 11π/6, 16π/6, 19π/6, 22π/6.