radius

Also known as circle radius, radius of a circle

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AI overview

A radius is a straight line drawn from the center of a circle to any point on its edge. It's an important measurement because it determines the size of the circle and is used to calculate other properties like the circle's area and distance around its edge.

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Wikidata facts

Image: Circle and radius el.svg

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Commons gallery: Radius

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~5 min read

Article

11 sections

Contents

Formula
Circles
Regular polygons
Hypercubes
Use in coordinate systems
Polar coordinates
Cylindrical coordinates
Spherical coordinates
See also
Notes
References

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In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is the line segment or distance from its center to any of its vertices. The name comes from the Latin radius, meaning ray but also the spoke of a chariot wheel. The typical abbreviation and mathematical symbol for radius is R or r. By extension, the diameter D is defined as twice the radius: