ρ=2sin(θ-π/4）
ρ^2=2ρsin(θ-π/4）
x^2 + y^2 = 2ρsinθcosπ/4-2ρcosθsinπ/4
x^2 + y^2 = √2ρsinθ - √2ρcosθ
x^2 + y^2= √2y - √2x
x^2 + √2x + y^2 - √2y =0
x^2 + √2x + 1/2 + y^2 - √2y +1/2 =1
(x+1/√2)^2 + (y-1/√2)^2 = 1
即圆心(-1/√2,1/√2)半径为1的圆
√2：2开平方 π 圆周率
应用公式：ρ^2 = x^2 + y^2
x=ρcosθ y=ρsinθ