Meaning of closed ball | Babel Free

Definitions

A ball which contains its boundary, i.e., a ball which is a closed set.

Examples

“In the set of 3-adic numbers, the closed ball of radius 1/3 "centered" at 1 is the set x|∃n∈ℤ.,x=3n+1. This closed ball partitions into exactly three smaller closed balls of radius 1/9, e.g., x|∃n∈ℤ.,x=4+9n. Then each of those balls partitions into exactly 3 smaller closed balls of radius 1/27, and the sub-partitioning can be continued indefinitely, in a fractal manner.”

CEFR level