Talk:Octagon

Are octagons necessarily convex? Isn't the only defining criterion that they have eight edges?

Since the description was explicitly referring to a "regular" octagon I think it would be correct to say that it can only be convex.

I removed the statement about convexity on May 27th. A general Octagon merely has 8 edges and could be concave, like a 4-sided star (like the central directions of a compass rose) could be considered a concave octagon. Agreed that a regular octagon (with equal turn angles) must be convex. --Tom Ruen 21:58, Jun 15, 2004 (UTC)

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I don't want to spoil anyone's fun, but that animation is really pretty and really dire. You cannot study it - it just flashes past. You cannot print it. What an encyclopaedic article wants is a set of diagrams, one after the other (in this case presumably 18 diagrams. I don't plan to do anything about it yet, but if I haven't received User_talk:SGBailey a reason not to, I plan to do such an edit at the beginning of March 2005. -- SGBailey 21:35, 2005 Feb 16 (UTC)

I don't have any trouble seeing the animation slowly enough to follow the steps. Perhaps there is an issue with your computer settings. If you want to convert it to eighteen pictures, I wouldn't object, but the single animation seems like a better, more compact illustration. -Willmcw 19:56, Feb 28, 2005 (UTC)

How about following the steps when you print the page out? -- SGB

Remember that wikipedia is not a "how-to" guide. It is interesting that a regular octagon can be created with only a compass and straight edge, and the animation is clear enough to duplicate. Why would anyone need to print it out? -Willmcw 21:18, Mar 2, 2005 (UTC)

Two more issues - these diagrams are taken from Euclid - maybe a link to a decent illustrated edition would be sufficient. Also, several of the regular polygons have similar animations. Are you proposing fixing all of them? -Willmcw 21:37, Mar 2, 2005 (UTC)

Confusion with undefined variable R and r

It mentions R (big r) and r (little) but doesn't say what it is. What does R and r mean? Thank you. 194.150.177.9 17:10, 16 October 2006 (UTC)

I believe that R is the circumradius (the radius of the circle that the octagon fits inside), and r is the inradius (the radius of the circle that fits inside the octagon). Hope that helps.

Ksiz 06:36, 10 December 2006 (UTC)

 ?

Before it said that it is sometimes called the "rectagon", but someone removed it with an edit summary of "deleted nonsense". Is it true that it is also called the "rectagon"? Kamope · talk · contributions 12:24, 17 January 2007 (UTC)

Yes, especially since rectagon redirects to this article. 86.170.145.158 (talk) 10:42, 5 July 2009 (UTC)

Somebody added a rectagon redirect [1] but not linked anywhere AND I've not seen any sources to support it. Tom Ruen (talk) 18:56, 5 July 2009 (UTC)

It appears to be a specific shape of Trampoline; a strectched octagon - but I can only find them made by one company, so it may be a trademark.[2] Would it be more useful redirecting to the trampoline article? 86.170.145.158 (talk) 23:39, 16 July 2009 (UTC)

Regular octagon

My eighth grade geometry teacher insisted than an octagon with equal length sides must be regular. I said no way and drew a flattened one out, one without congruent angles. But I didn't know how to prove it. Please tell me I was right. Okay, I'm done now. ---Ransom (69.105.95.130 03:23, 28 February 2007 (UTC))

You're right. Equal side lengths isn't enough--the angles need to be equal, too. Since equilateral doesn't imply equiangular (except for triangles), it doesn't imply that the polygon is regular, either. --Sopoforic 06:00, 28 February 2007 (UTC)

Correct formula?

MOVED FROM PAGE:

In terms of $R$, (circumradius) the area is $8R^2/(1+\sqrt{2})$ THIS IS INCORRECT!

Comments should be on talk, not in article. Well, I'll put a { { fact } } mark on it for now.

Can anyone confirm this formula? Tom Ruen 20:27, 28 March 2007 (UTC)

A hexagon

A hexagon has 6 sides on its shape —Preceding unsigned comment added by 69.250.132.155 (talk) 00:35, 30 May 2008 (UTC)

Derivation

There was a derivation of the area attributed to Archimedes that appeared to be utter nonsense. I removed it.

I cleaned up the current derivation, but it needs more work and a diagram. Hopefully I'll be able to make and upload a good diagram within the next couple of days. —Preceding unsigned comment added by Talldave (talk • contribs) 02:27, 15 June 2008 (UTC)

R and r

It would be nice to include formulas for r and R in terms of a. Ccrrccrr (talk) 14:59, 27 August 2010 (UTC)

I agree. I think these should come before the area formulas. Shall I add them? Dbfirs 18:23, 27 August 2010 (UTC)