原式= sinx/√(1+(2cos²(x/2)-1)= 2sin(x/2)cos(x/2)/√2|cos(x/2)|x趋于π加,x/2趋于π/2加,cos(x/2)在第二象限为负值所以,原值=-2sin(x/2)cos(x/2)/√2cos(x/2)=-√2sin(x/2)=-√2sin(π/2)=-√2...