ρ=2cos(x-π/4)=√2cosx+√2sinx
∴ρ²=√2ρcosx+√2ρsinx
∴x²+y²=√2x+√2y

ρ=2sin(x-π/4)=√2sinx-√2cosx
∴ρ²=√2ρsinx+√2ρcosx
∴x²+y²=√2y+√2x