Construction of a pentagon using only the grid system

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Discussion Overview

The discussion revolves around the construction of a pentagon using only a grid system, exploring the accuracy of internal angles and the implications of such a construction without traditional tools like a compass or trigonometry. Participants share their methods and thoughts on the significance of the discovery.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant claims to have constructed a pentagon with internal angles within 99% accuracy, asserting that the angles add up to 540 degrees without using a compass.
  • Another participant describes their attempt to construct a pentagon using compass and straight-edge rules, translating them into a grid system without trigonometry.
  • A later reply questions the relevance of the construction, suggesting that approximate constructions have not been significant in mainstream mathematics for decades.
  • One participant emphasizes that the internal angles of any pentagon will always sum to 540 degrees, referencing a mathematical resource.
  • Another participant expresses confusion regarding the distinction between using a grid and traditional construction methods, seeking clarification on the original method described.
  • One participant suggests that the grid-based construction could have practical applications in nature, such as modeling pentagonal structures found in starfish or flowers.
  • Another participant challenges the accuracy of the angles in the previous construction attempts and requests more details about the methods used.
  • One participant asserts that their construction method, which took 14 years to develop, results in a pentagon with a specific accuracy of 99.39% for the lowest angle shared by two angles.

Areas of Agreement / Disagreement

Participants express differing views on the significance and accuracy of the pentagon construction methods discussed. There is no consensus on the value of the discovery or the effectiveness of the various approaches presented.

Contextual Notes

Some participants note the challenge of achieving a perfect pentagon using only a grid system, and there are unresolved questions regarding the accuracy of angles and the methods employed in the constructions.

Scotti G
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I have found a way to construct a pentagon using only the grid system. The internal angles are all within 99% accuracy and all the angles to the 3rd decimal add up exactly to 540 degrees. This is without the use of a compass and bearing in mind that the internal lines intersect at the ration of phi, it is theoretically impossible to construct a perfect pentagon. Is this "discovery" of any value or consequence?
 
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If we are talking about the same thing, I think this is something I tried to do as well. I started with the rules for a compass and straight-edge construction of a pentagon. Then I put the apex on the y-axis and the two adjacent vertices on the x. Then I 'translated' the construction rules into triangles, and then I just went to town pythagorean style. My goal was to do it without using trig. Is this something like what you did?
 
Thread moved to General Math.
 
Scotti G said:
Is this "discovery" of any value or consequence?

Not really. It's a neat curiosity though. Maybe you'll even get it published in a journal on Euclidean geometry. But these kinds of constructions (especially approximate ones) haven't been important to mainstream mathematics for decades.
 
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Scotti G said:
The internal angles are all within 99% accuracy and all the angles to the 3rd decimal add up exactly to 540 degrees.
Internal angles of any 5 edged polygons (pentagons as well as any iregular 5 edged shape) will always add up to precisely 540 degrees.

http://www.mathsisfun.com/geometry/interior-angles-polygons.html
 
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Terribly sorry to mention it, but this thread is not about constructing a pentagon using a straight edge and compass. It is (I think) about identifying the Cartesian coordinates which would lie on a circle, and would correspond to the vertices of a regular pentagon without the use of trig.

Of course, for all I know, it could be ridiculously simply to do what I described and Scotti G might be talking about something completely different. But the OP has not checked in since posting, so no clarification on that score yet.
 
Yes my goal was to construct a pentagon without trig or the use of a compass. What was the accuracy of you angles with your construction? If you say you
started with the rules for a compass and straight-edge construction of a pentagon then you "tried" it without trig but not without a compass.
On a different subject I think my "discovery" could very well be used in nature to construct pentagonal structures such as starfish or flowers as the construction using only a grid system is far more plausible than the use of trig or a compass at atomic level.
 
I didn't really get that far. And now I'm confused by what you mean by 'without a compass.' Any chance you could share what you did? At least describe it in more detail?
 
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I simply used only the grid system. No trig. no compass. no protractor. " I started with the rules for a compass and straight-edge construction of a pentagon" - you. I started only with the grid and my pip. It took 14 years of persistence but the construction only has 7 lines and you have a pentagon with all the angles within 99% accuracy, to be precise the lowest accurate angle shared by 2 angles is 99.39%. I don't believe a more accurate pentagon could be constructed using only the x and y axis.
 

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