y=cos(2x-3π/4)-2√2(sinx)^2
=cos(2x-3π/4)+√2[1-2(sinx)^2]-√2
=-√2/2*cos2x+√2/2*sin2x+√2cos2x- √2
=√2/2*cos2x+√2/2*sin2x-√2
=cos(2x-pi/4)-√2
T=2pi/2=pi