If a regular polygon has a fixed edge length, can I know how many edges it has by knowing the length from corner to its center?

Aydin Jarvis

Aydin Jarvis

Answered question

2022-10-18

How do I get an integer from a polygon equation, which usually returns fractions?
Known: edge length
Unknown: number of edges
Radius should increase of decrease to an interval to ensure number of edges in Polygon is divisible by 1
E.g. edge length is 100mm, number of edges unknown, radius is 6m. How do I find the closest radius to 6m which gives an integer, divisible by 1, for a realistic number of edges.
Previous Question
If a regular polygon has a fixed edge length, can I know how many edges it has by knowing the length from corner to its center?
and it's answer
the radius of the polygon, and it has the formula
r = s 2 sin ( 180 ° n )
where s is the side length of the polygon and n is the number of sides. So given r and s, you can simply solve the above equation for n.
It's worth pointing out that when you solve for n there's no guarantee that it will turn out to be an integer, and hence correspond to a regular polygon
I have no math background, not even enough to know which tags to attach. How do I solve for these intervals of radii?

Answer & Explanation

Layne Murillo

Layne Murillo

Beginner2022-10-19Added 14 answers

Step 1
Rearrange your formula for r in terms of n n = π arcsin ( s 2 r ) 2 π r s for  r s and insert the desired values.
Step 2
For your example n 2 π 6  m 0.1  m 377 is very close
n 376 377 378 r  in m 5.9843 6.0002 6.0161

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