y=sinx+cos(x+π/6)
=sin[(x+π/6)-π/6]+cos(x+π/6)
=sin(x+π/6)cosπ/6-cos(x+π/6)sinπ/6+cos(x+π/6)
=√3/2sin(x+π/6)-1/2cos(x+π/6)+cos(x+π/6)
=√3/2sin(x+π/6)+1/2cos(x+π/6)
=sin(x+π/6+π/6)
=sin(x+π/3)
∴周期T=π/3.
y=sinx+cos(x+π/6)
=sin[(x+π/6)-π/6]+cos(x+π/6)
=sin(x+π/6)cosπ/6-cos(x+π/6)sinπ/6+cos(x+π/6)
=√3/2sin(x+π/6)-1/2cos(x+π/6)+cos(x+π/6)
=√3/2sin(x+π/6)+1/2cos(x+π/6)
=sin(x+π/6+π/6)
=sin(x+π/3)
∴周期T=π/3.