1/2=sin(π/6),√3/2=cos(π/6),因此可对表达式化简:
y=(1/2)(cosx)^2+(√3/2)sinxcosx+1
=cosx[sin(π/6)cosx+cos(π/6)sinx]+1
=sin(x+π/6)cosx+1 ………………………………………………………(1)
sin(2x+π/6)=sin(x+π/6+x)=sin(x+π/6)cosx+cos(x+π/6)sinx ………(2)
1/2=sin(π/6)=sin(x+π/6-x)=sin(x+π/6)cosx-cos(x+π/6)sinx ………(3)
(2)+(3)可得:sin(x+π/6)cosx=[sin(2x+π/6)]/2+1/4 ……………(4)
把(4)代入(1)继续化简:
sin(x+π/6)cosx+1
=[sin(2x+π/6)]/2+1/4+1
=[sin(2x+π/6)]/2+5/4
因此:y=[sin(2x+π/6)]/2+5/4
y取最大值时,sin(2x+π/6)=1,即2x+π/6=2kπ+π/2,求得x=kπ+π/6(k∈Z),
因此所求x的集合为:{x|x=kπ+π/6(k∈Z)}