Talk:Unit disk

From Wikipedia, the free encyclopedia
Jump to: navigation, search

Prove that the ratio of the circumference to the diameter of a unit disc is always in between 3 and 4. Hint: These values are attained when the unit disc is a regular hexagon resp. a square (i.e. for the sup norm). — MFH:Talk 14:45, 23 March 2006 (UTC)

Perimeter: Disc or circle?[edit]

I'm not sure the paragraph about the perimeter is relevant to this article. As far as I know, perimeter is a property of the unit circle, and not the unit disc. Maybe you'll add it there instead? -- Meni Rosenfeld (talk) 15:39, 24 March 2006 (UTC)

Opaque[edit]

(was: Area = π?) I smell a rat. John Reid 18:04, 5 April 2006 (UTC)

What seems to be the problem? -- Meni Rosenfeld (talk) 06:53, 6 April 2006 (UTC)

Okay, after the 8th or 9th re-reading, I begin to grasp the topic -- a little. I have had personal experience with the taxicab metric, having once created a map inset graphic defining the limits of the concept "within N blocks".

I retract the rat, but boy, this article is opaque. Needs rewrite for general audience. John Reid 20:19, 7 April 2006 (UTC)

i'm no matematician, nor math student at all, but wasn't the area of a circle πR² ? capi 10:43, 24 April 2006 (UTC)
Yup, it was and is :-) So if the radius is 1, as is the case for the unit disc, you get an area of π. AxelBoldt 20:06, 24 April 2006 (UTC)

Golab's theorem?[edit]

In 1932, S. Gołąb proved that the perimeter of the unit disc can take any value in between 6 and 8

What is the precise statement of this theorem? I can easily give a metric on R2 whose unit disc is equal to R2 and the perimeter (defined as the unit disc's boundary) is therefore empty. AxelBoldt 19:20, 16 April 2006 (UTC)

I thought I clarified this, but apparently, I did not. According to the article mentioned in the External links section, it should be a metric that arises from a norm. I edited the article to make it at least a bit clearer. Thanks, Jitse Niesen (talk) 06:21, 18 April 2006 (UTC)

Spelling[edit]

Should this article be moved to Unit disk to be consistent with Disk (mathematics)? -- Meni Rosenfeld (talk) 16:31, 28 April 2006 (UTC)

What's the issue here? Is this a British vs. American English thing? AxelBoldt 03:46, 29 April 2006 (UTC)

Yes, Disk (mathematics) uses British (k), and this one, Unit Disc, uses American (c). Not that it matters this much, but I thought it would be good to have them consistent with each other, especially since they link to each other. -- Meni Rosenfeld (talk) 14:42, 29 April 2006 (UTC)

I don't have an opinion on the move, but I can tell you these things go on forever and never settle down. You change it now, in half a year someone else will change it back. AxelBoldt 18:24, 29 April 2006 (UTC)

Inverse function[edit]

The article states that is bijective, although Wolfram gives two solutions. Either the statement is false, or the author took a branch of the root. In either case I'm not sure what the policy on Wikipedia (or its math community) is on how to correct such things, as the article obviously should not be bloated. 145.107.16.149 (talk) 08:57, 2 March 2015 (UTC)

External links modified[edit]

Hello fellow Wikipedians,

I have just modified one external link on Unit disk. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Sourcecheck}}).

You may set the |checked=, on this template, to true or failed to let other editors know you reviewed the change. If you find any errors, please use the tools below to fix them or call an editor by setting |needhelp= to your help request.

  • If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
  • If you found an error with any archives or the URLs themselves, you can fix them with this tool.

If you are unable to use these tools, you may set |needhelp=<your help request> on this template to request help from an experienced user. Please include details about your problem, to help other editors.

Cheers.—InternetArchiveBot (Report bug) 20:22, 20 July 2016 (UTC)