偶函数则满足：f（-x）=f（x）周期函数则满足：f(x)=f(x+π)f（11π / 3）=f(2π/3 +3π)=f(2π/3)f(2π/3)=f(2π/3-π)=f(-π/3)因为是偶函数f(-π/3)=f(π/3)x属于【0，π/2】时，f（x）=sin2x代入则有f（x）=sin2x=根号（3）/2
