圆普通方程怎么化极坐标方程?

(x-a)^2+(y-b)^2=r^2[(x-a)/r]^2+[(y-b)/r]^2=1设(x-a)/r=cosα,(y-b)/r=sinαx-a=rcosα,y-b=rsinαx=a+rcosα,y=b+rsinα