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Circumference
Perimeter of a circle or ellipse / From Wikipedia, the free encyclopedia
For the circumference of a graph, see Circumference (graph theory).
In geometry, the circumference (from Latin circumferens, meaning "carrying around") is the perimeter of a circle or ellipse.[1] The circumference is the arc length of the circle, as if it were opened up and straightened out to a line segment.[2] More generally, the perimeter is the curve length around any closed figure. Circumference may also refer to the circle itself, that is, the locus corresponding to the edge of a disk. The circumference of a sphere is the circumference, or length, of any one of its great circles.
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circumference C
diameter D
radius R
center or origin O
Circumference = π × diameter = 2π × radius.