解你好是ρcos(θ−π /4)=2√2吧
即p（cosθcosπ/4+sinθsinπ/4)=2√2
即pcosθcosπ/4+psinθsinπ/4=2√2
即x*√2/2+y*√2/2=2√2
即x+y=4
即x+y-4=0