则会得到一个正交双曲线，原点与它最接近的点之间的距离是 r。

You will have drawn a rectangular hyberbola whose point of closest approach to the origin is r.

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如定义：“平面内到两个定点的距离的差的绝对值等于常数的点的轨迹是双曲线。”

If the definition: "the plane's two fixed-point distance of the poor in absolute terms equal to the constant point of the track is hyperbolic."

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