Disk (mathematics)

In geometry, a disk (also spelt disc) is the region in a plane bounded by a circle. A disk is said to be closed or open according to whether or not it contains the circle that constitutes its boundary. In Cartesian coordinates, the open disk of center and radius R is given by the formula while the closed disk of the same center and radius is given by The area of a closed or open disk of radius R is πR2 (see π).
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