y=sin(x+π/6)+sin(x-π/6)+cosx ,x∈[-π/2,π/2]的值域
问题描述：
y=sin(x+π/6)+sin(x-π/6)+cosx ,x∈[-π/2,π/2]的值域
答
y=sinxcosπ/6+cosxsinπ/6+sinxcosπ/6-cosxsinπ/6+cosx
=√3sinx+cosx
=2(sinx√3/2+cosx*1/2)
=2(sinxcosπ/6+cosxsinπ/6)
=2sin(x+π/6)
-π/3