The Unit ball reference article from the English Wikipedia on 24-Jul-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Unit ball

In mathematics, the open unit ball in a normed vector space for a given norm is

.

The closed unit ball on under is

.

The 'shape' of the unit ball is entirely dependent on the chosen norm; it may well have 'corners', and for example may look like [−1,1]ⁿ, in the case of the norm l_∞ in Rⁿ.

See also:

• unit circle
• unit square
• unit disk
• sphere
• ball (mathematics)
• Table of mathematical symbols

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