已知函数y=2sin^2(x+4/π)-[根号3(cos2x)],x∈[4/π,2/π],求y的最大,小值//

y=2sin²(x+4/π)-[√3(cos2x)],
=[1-cos(2x+π/2)]-[√3(cos2x)]
=(1+sin2x)-[√3(cos2x)]
=2sin(2x-π/3)+1
x∈[4/π,2/π],2x-π/3∈[π/6,2π/3]
y的最大f(5π/12)=3,最小值f(π/4)=f(π/2)=2