f(x)=2√2sinxcosx+2√2cos(x+π/4)cos(x-π/4) =√2sin2x-2√2sin(x+π/4-π/2)cos(x-π/4) =√2sin2x-√2sin(2x-π/2) =√2sin2x+√2cos2x =2sin(2x+π/4)