52.还有一题DS, 在坐标轴里能不能确定个圆, (1).次圆过(2,0) 及(0,2)两点. (2). 圆的半径小于等于跟号2. 我选C 不确定.
选c
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from (1) the distance of the points is 2 *square root of 2<=diameter of the circle, from (2) the diameter <= 2*square root of 2, so the line segment between the two points is the diameter of a circle.
so the circle is determined. | 
