y=sin(x+π/3)+cos(x+π/6)
=sin(x+π/3)+sin(π/2-x-π/6)
=sin(π/3+x)+sin(π/3-x)
=sinπ/3cosx+cosxsinπ/3+sinπ/3cosx-sinπ/3cosx
=2sinπ/3cosx
=√3cosx (cosx