Talk:Ball (mathematics)

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Use of "interior"[edit]

There are several instances in the current article where the ball is referred to as the "interior" of the sphere. Unfortunately "interior" also means something distinct in a context very near this one; specifically the (topological) interior of any set is the largest open set contained in that set. In particular, the (topological) interior of the closed ball is the open ball. Importantly, the $(n -1)$ -dimensional sphere interpreted as embedded $n$ -dimensional space has the empty set as its (topological) interior. Instead interpreting the $(n -1)$ -dimensional sphere as its own manifold gives the entire $(n -1)$ -dimensional sphere as its own (topological) interior. Either way, the (topological) interior of the sphere is not the ball. Is anyone else concerned about this? Should we change the article to either avoid the use of "interior" or to clarify that it is not the topological interior that is meant? 𝕃eegrc (talk) 14:08, 9 December 2015 (UTC)[reply]

Math markup bug[edit]

The end of the sentence "The closure of the open ball $B r (p)$ is usually denoted $B r (p)$ " appears incorrectly. There should just be one horizontal line over the entire expression $B r (p)$ , rather than a separate horizontal line over each letter. It's not obvious to me how to get the desired behavior using the existing markup language. I'm not sure where to report bugs in the markup language, if there is somewhere please let me know. David9550 (talk) 11:06, 19 January 2018 (UTC)[reply]

open ball[edit]

Is it related to meteric spaces? 2409:4055:210:3DBB:A7FF:39E6:636E:D2B0 (talk) 03:45, 8 December 2021 (UTC)[reply]