求函数y=cosx+cos(x-π/3)的最大值

y=cosx+cos(x-π/3)
=cosx+cosxcos(π/3)+sinxsin(π/3)
=(3/2)cosx+(√3/2)sinx
=√3* [cosx*(√3/2)+sinx*(1/2)]
=√3[cosxsin(π/3)+cosxsin(π/3)]
=√3sin(x+π/3)
所以函数y=cosx+cos(x-π/3)的最大值为√3