f(x)=sin2x-cos2x =√2*[sin2x*(√2)/2 - cos2x*(√2)/2] =√2*[sin2x*cos(π/4) -cos2x*sin(π/4)] =√2*sin(2x-π/4)
f(x)=sin2x—cos2x=sin2xcos(π/4)—cos2xsin(π/4)=√2sin(2x-π/4)
