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Ford circle
Rational circle tangent to the real line / From Wikipedia, the free encyclopedia
In mathematics, a Ford circle is a circle in the Euclidean plane, in a family of circles that are all tangent to the -axis at rational points. For each rational number
, expressed in lowest terms, there is a Ford circle whose center is at the point
and whose radius is
. It is tangent to the
-axis at its bottom point,
. The two Ford circles for rational numbers
and
(both in lowest terms) are tangent circles when
and otherwise these two circles are disjoint.[1]
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