sin(x+π/3)+（tanπ/6）cos(x+π/3)
=1/cosπ/6（sin(x+π/3)*cosπ/6 + cos(x+π/3) sinπ/6）
=2√3/3 *sin(x+π/3+π/6）=2√3sin(x+π/2）/3=2√3cosx/3