The Wayback Machine - https://web.archive.org/web/20140326021130/http://mathworld.wolfram.com/Disk.html

Disk

DOWNLOAD Mathematica Notebook

An n-dimensional disk (sometimes spelled "disc") of radius r is the collection of points of distance <=r (closed disk) or <r (open disk) from a fixed point in Euclidean n-space. A disk is the shadow of a ball on a plane perpendicular to the ball-radiant point line.

The n-disk for n>=3 is called a ball, and the boundary of the n-disk is a (n-1)-hypersphere. The standard n-disk, denoted D^n (or B^n), has its center at the origin and has radius r=1.

Wolfram Web Resources

Mathematica »

The #1 tool for creating Demonstrations and anything technical.

Wolfram|Alpha »

Explore anything with the first computational knowledge engine.

Wolfram Demonstrations Project »

Explore thousands of free applications across science, mathematics, engineering, technology, business, art, finance, social sciences, and more.

Computable Document Format »

The format that makes Demonstrations (and any information) easy to share and interact with.

STEM initiative »

Programs & resources for educators, schools & students.

Computerbasedmath.org »

Join the initiative for modernizing math education.