求函数y=sinx/2(sin x/2-cos π/2)的最大值和最小值

y=sinx/2(sin x/2-cos x/2) =sin²x/2-sinx/2*cos π/2 =½(1-cosx)-½sinx =-½(sinx+cosx)+1/2 =-√2/2sin(x+π/4)+1/2 当sin(x+π/4)=1时，y=sinx/2(sin x/2-cos x/2)有最小值：（-√2+1）/2 当sin(x+