y = sin(2x + π/3) + sin(2x - π/3) + 2cos²x= sin2xcosπ/3 + cos2xsinπ/3 + sin2xcosπ/3 - cos2xsinπ/3 + （2cos²x-1） + 1= 2sin2xcosπ/3 + cos2x + 1=sin2x + cos2x + 1=根号2sin（2x + π／4）...