sin2x/3+cos2x/3=√2 X（√2/2 X sin2x/3+√2/2 X cos2x/3) =√2 X (cosπ/4 Xsin2x/3+sinπ/4 X cos2x/3) =√2 X sin(2x/3+π/4）即sinx X cosy+cosx X siny=si...