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April 19th, 2013, 06:57 AM   #1
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The Protractor - Its Construction

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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 straight-edge-and-compass exact.

So how are modern and ancient protractors marked exactly? Or is it exact?
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April 20th, 2013, 06:03 AM   #2
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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
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April 20th, 2013, 06:16 AM   #3
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Re: The Protractor - Its Construction

Do you mean the highest common multiple of 3, 4, 5 and 6?
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April 20th, 2013, 06:32 AM   #4
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Re: The Protractor - Its Construction

Quote:
Originally Posted by Hoempa
Do you mean the highest common multiple of 3, 4, 5 and 6?
Yes. But those are are not just numbers. They are analog fractions of a circle.
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April 20th, 2013, 06:43 AM   #5
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Re: The Protractor - Its Construction

There are infinitely many numbers higher than 360 that are a multiple of 3, 4, 5 and 6.
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April 21st, 2013, 05:53 AM   #6
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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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