易得圆x^2 +y^2 =b^2
点到直线距离方程|x-y+2|/√(1^2 +1^2)
圆心(0,0)代入有|2|/√(1^2 +1^2) = b
得b^2 =2
e^2 =1/3
解得a^2 = 3 c^2= 1
即x^2/3 +y^2/2 =1
易得圆x^2 +y^2 =b^2
点到直线距离方程|x-y+2|/√(1^2 +1^2)
圆心(0,0)代入有|2|/√(1^2 +1^2) = b
得b^2 =2
e^2 =1/3
解得a^2 = 3 c^2= 1
即x^2/3 +y^2/2 =1