y=sin (2x+30)+sin(2x-30)+cos2x+a =sin2xcos30+cox2xsin30+sin2xcos30-cos2xsin30+cos2x+a = 根号3 sin2x+cos2x+a = 2(根号3/2 sin2x + 1/2cos2x) +a = 2sin(2x+30)+a
故 最小正周期 pi 单调减区间为 2kpi+pi/2
y=sin (2x+30)+sin(2x-30)+cos2x+a =sin2xcos30+cox2xsin30+sin2xcos30-cos2xsin30+cos2x+a = 根号3 sin2x+cos2x+a = 2(根号3/2 sin2x + 1/2cos2x) +a = 2sin(2x+30)+a
故 最小正周期 pi 单调减区间为 2kpi+pi/2