f(x)=CosX+Cos(x+兀/3)
=cosx+cosxcosπ/3-sinxsinπ/3
=3/2cosx-√3/2sinx
=√3(√3/2cosx-1/2sinx)
=√3cos(x+π/6)
最大值为√3,最小值为-√3
（2）
f(X)=SinX+根号Cosx
=2（1/2sinx+√3/2cosx)
=2sin(x+π/3)
∵x∈[-π/2,π/2]
∴x+π/3∈[-π/6,5π/6]
∴sin(x+π/3)∈[-1/2,1]
∴2sin(x+π/3)∈[-1,2]
即函数最大值为2,最小值-1