x＾2+y＾2-4rxcosA-4rysina+3r＾2=0(r>0),当A固定,r变动时,求圆心的轨迹方程“

x＾2+y＾2-4rxcosA-4rysina+3r＾2=0(r>0),当A固定,r变动时,求圆心的轨迹方程“

化简得
（x-2rcosA)^2+(y-2rsinA)^2=r^2
圆心坐标为X=2rcosA Y=2rsinA
X^2+Y^2=4r^2