F(x)=4sinx[sin（π／4＋x/2)的平方〕＋cos2x
=2sinx[1+sinx]＋cos2x
=2sinx+2sin^2x+1-2sin^2x=1+2sinx
π／6<=x<=2π／3 2<=F(x)<=3 题目不完整需要补充