Talk:Hendecagon

What is the Susan B Anthony Dollar? Thanks! Mark Richards 21:24, 14 May 2004 (UTC)

A Susan B Anthony coin is a US one-dollar coin, right? One of those annoying special edition things. I'm not entirely sure. Agkeene 05:06, 16 February 2006 (UTC)

It was regular currency for several years and was very unpopular. Most people didn't like to use them because they were too similar in size to the quarter-dollar (and Anthony was homely). The Sacagawea dollar works much better, although people don't generally use it as pocket change.--Syd Henderson 20:22, 20 August 2006 (UTC)

Indeed a word of Greek origin

Hendecagon is indeed a word phonetically derived from the greek "Ενδεκάγωνο". I.e. Ένδεκα(Hendeca)=11 and γωνία(gonia)=angle. The final -ia drops out in the English word to facilitate pronunciation. Also in modern Greek the leading "H" is silent. In ancient Greek it sounded more kind of todays English, like a soft "H"

(Note: In order for your browser to properly display the Greek text you need to select the Unicode (UTF-8) encoding. Mind you that when the "Eastern European (Windows)" encoding is selected (it is the default selection in the US) the Greek text will not be properly displayed.)

Thank you,

Dimitrios G. Panagiotidis
Chicago, IL - USA.

Equation extends off page

Math equation extends far off page. Can anyone look into a way of fixing this? Beyond my scope. — Preceding unsigned comment added by Jhahner18 (talk • contribs) 02:14, 10 January 2019 (UTC)

This edit was the culprit. Fixed, thanks. Don't know why nobody else noticed in a year and a half. —David Eppstein (talk) 05:23, 10 January 2019 (UTC)

Exact construction

I found a hendecagon construction on r/neusis that seems to be exact but uses a funny circle tool, is that still a neusis Codeapotamus (talk) 23:21, 12 April 2025 (UTC)

A hendecagon can't be constructed exactly with compass-and-straightedge, because the order of its Galois group - Phi(11)=10 - is not a power of two. Just as for septagon and nonagon (Phi(7) and Phi(9) both equal 6); the latter forming part of Galois Theory's proof for the non-trisectability of arbitrary angles by c&s.

Interestingly, I recall reading that the use of origami folds allows for Galois groups including a power of three as well as two. (There's a sort of sliding operation that effectively constructs a cube root.) That makes the hendecagon (10=2x5) the smallest regular polygon that can't be constructed exactly by origami folds. Worth noting on the page perhaps?

Source for constructibility criterion: https://digitalworks.union.edu/theses/2299/ - note especially the list of origami-constructible shapes at the bottom of page 36. 2A02:6B6F:E921:5700:BDA8:7B99:7052:F8DE (talk) 10:51, 22 June 2025 (UTC)

The cited origami article includes a method, unlike the neusis proof article. Reepy1 (talk) 05:57, 27 September 2025 (UTC)

Hi, I've been wondering the exact same thing. I'm not sure if that Reddit construction counts because of the funny circle tool; but if someone manages to simplify the funny circle tool to a marked ruler, then it would count; otherwise, we need to find another method... Also, the cited origami article includes a method, unlike the neusis proof article.

That Reddit user claims the 25-gon is also possible with that tool, Wikipedia says 25-gon's neusis constructibility is unknown. Reepy1 (talk) 05:57, 27 September 2025 (UTC)