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Subject: 
Re: How to make a perfect octagon or hexagon?
Newsgroups: 
lugnet.technic, lugnet.edu
Followup-To: 
lugnet.edu
Date: 
Mon, 10 Dec 2007 16:32:51 GMT
Viewed: 
20276 times
  
In lugnet.technic, Joe Strout wrote:

   I’m trying to make a largish... octagon or hexagon out of technic parts.

A 12-12-17 triangle is very nearly right, and has angles of about 44.9 degrees. I used four of them in making a stop sign:



Note that all eight corners are nicely studded down.

Joe and Brian wrote:

  
   I believed that the bent technic beams... had a 135-degree angle, or at least some angle that would divide evenly into 360.

They do (sort of, some of them), but it might not be in the way you’re using them:

http://technic.lego.com/technicdesignschool/lesson.asp?x=x&id=1_c&page=3

Well whaddaya know! I’d always assumed those things were 135 degrees. Looks like I learned something today. Brian, many thanks for the terrific Lego geometry links I did not know about. You made my day.

Brian Davis wrote:

   The internal angles on a 3-4-5 right triangle are 30, 60, and of course 90 degrees.

And now a teachable moment! You’ve made my week! As DaveE alludes elsewhere in this thread, a 3-4-5 triangle has angles of about 36.87, 53.13, and 90 degrees. Making one of these triangles is a great way to build a strong right angle. A triangle with angles of 30, 60, and 90 degrees is a different animal: half an equilateral triangle. It can help in making a regular hexagon. Unfortunately, at least one of its sides must have a funny (irrational) length, so it isn’t the easiest thing to build in brick or technic.

-Teddy


p.s. I must admit that when I first read Brian’s statement, I made a noise so horrible my colleagues here in the math department wondered if I was ill. Don’t worry. I’ll be fine. Eventually.



Message has 1 Reply:
  Re: How to make a perfect octagon or hexagon?
 
(...) Yeah, about 5 minutes after I submitted that I realized just how stupid I've become as of late (I plead mercy due to a very nasty sinus infection... but dang it, I should have caught that even if I was unconcious). What will make it even (...) (16 years ago, 10-Dec-07, to lugnet.edu)

Message is in Reply To:
  Re: How to make a perfect octagon or hexagon?
 
(...) Try approaching it in steps. Can you make an equilateral triangle out of Technic beams? Don't worry about making the angles rigid, just make a structure with three equal-length sides, connected near the corners (connected with something that (...) (16 years ago, 10-Dec-07, to lugnet.technic)

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