由(sinx-cosx)^2=1-2sinxcosxsinxcosx=[1-(sinx-cosx)^2]/2令sinx-cosx=t t=√2sin(x-π/4) -1≤t≤√2y=sinxcosx+sinx-cosx=(1-t^2)/2+t=-t^2/2+t+1/2=-1/2(t-1)^2+1对称轴t=1y在[-1,1]上单调递增在[1,√2]上单调递...