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How is the curvature of a circle related to its radius?

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In differential geometry, the curvature of a circle is defined as the reciprocal of its radius, expressed as 1r.12

This relationship signifies that as the radius of a circle increases, the circle becomes straighter and its curvature decreases. Conversely, a smaller radius results in a higher degree of curvature. In the limit, a straight line is considered a circle with an infinite radius, resulting in a curvature of zero. This concept is fundamental to the study of curvature, where the osculating circle—the circle that most closely approximates a curve at a given point—is used to define the curvature of more complex shapes.21