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April 19th, 2013, 07:57 AM  #1 
Banned Camp Joined: Feb 2013 Posts: 224 Thanks: 6  The Protractor  Its Construction
This topic is a continuation of this topic. viewtopic.php?f=13&t=18374#p163581 Who invented the 360 degrees protractor? When? How? How is it possible to divide a circle into 360 parts? The only way I know how is to divide it down to 3 degrees, but no way to divide it down to 1 degree, not straightedgeandcompass exact. So how are modern and ancient protractors marked exactly? Or is it exact? 
April 20th, 2013, 07:03 AM  #2 
Banned Camp Joined: Feb 2013 Posts: 224 Thanks: 6  Re: The Protractor  Its Construction
Why? My guess. Highest common multiple of constructible polygons. Triangle, Square, Pentagon, Hexagon. 3 x 4 x 5 x 6 = 360 
April 20th, 2013, 07:16 AM  #3 
Math Team Joined: Apr 2010 Posts: 2,778 Thanks: 361  Re: The Protractor  Its Construction
Do you mean the highest common multiple of 3, 4, 5 and 6?

April 20th, 2013, 07:32 AM  #4  
Banned Camp Joined: Feb 2013 Posts: 224 Thanks: 6  Re: The Protractor  Its Construction Quote:
 
April 20th, 2013, 07:43 AM  #5 
Math Team Joined: Apr 2010 Posts: 2,778 Thanks: 361  Re: The Protractor  Its Construction
There are infinitely many numbers higher than 360 that are a multiple of 3, 4, 5 and 6.

April 21st, 2013, 06:53 AM  #6 
Banned Camp Joined: Feb 2013 Posts: 224 Thanks: 6  Re: The Protractor  Its Construction
I found the answer. You can't draw 1 degree with straight edge and compass. viewtopic.php?f=13&t=18374&p=163757#p163757 

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