Disk (mathematics)
In geometry, a disk is an n-dimensional region, in Euclidean space, bounded by an (n−1)-dimensional hypersphere. The everyday usage corresponds to n = 2, namely the inside of a circle in the plane
A representative disk is three-dimensional volume element of a solid of revolution. The element is created by rotating a line segment (of length "w") around some axis (located "r" units away); such that, a cylindrical volume, of π∫r2w units, is enclosed.
A disk is said to be closed or open according to whether the region does or does not include its boundary. A ball is a disk in a space with more than two dimensions. See ball (mathematics). In particular, in a two dimensional Euclidean space, an open (respectively closed) disk is a circular area without (resp. with) its boundary circle.
In topology, a open disk and a closed disk in a metric space are synonymous with an open ball and closed ball.
See also:
