已知实数X,Y满足：X-Y大于等于0 X+Y-1小于等于0 Y+1大于等于0,(X,Y)在...已知实数X,Y满足：X-Y大于等于0 X+Y-1小于等于0 Y+1大于等于0,若点P(X,Y)在圆x^2+(y-1)^2=a(a>0)的内部或圆上,则a的最小值为为多

已知实数X,Y满足：X-Y大于等于0 X+Y-1小于等于0 Y+1大于等于0,(X,Y)在...
已知实数X,Y满足：X-Y大于等于0 X+Y-1小于等于0 Y+1大于等于0,若点P(X,Y)在圆x^2+(y-1)^2=a(a>0)的内部或圆上,则a的最小值为为多少?
希望有过程 谢谢

Y+1>=0 Y>=-1
X-Y>=0 X>=Y
X+Y-1

a>=2