y=2sin(x-π/4)cos(x+π/4)+1
=2sin(x-π/4)sin[π/2-(x+π/4)]+1
=2sin(x-π/4)sin(π/4-x)+1
=-2sin²(x-π/4)+1
=-[1-2sin²(x-π/4)]
=-cos[2(x-π/4)]
=-cos(2x-π/2)
=-sin2x