区间是-2/π还是-π/2 我算-π/2
f(x)=√2*[sin(π/4)cos2x-cos(π/4)sin2x]
=√2*sin(π/4 -2x)
x∈[-π/2,0],π/4-2x∈[π/4,5π/4]
x=-π/8时,f(x)max=√2
x=-π/2时,f(x)min=-1