SOLUTION: In the figure below, the innermost circle has radius 1. It is circumscribed by an equilateral triangle, which is circumscribed by a circle, which is circumscribed by a square,

Algebra ->  Circles -> SOLUTION: In the figure below, the innermost circle has radius 1. It is circumscribed by an equilateral triangle, which is circumscribed by a circle, which is circumscribed by a square,       Log On


   



Question 1031251: In the figure below, the innermost circle has radius 1.
It is circumscribed by an equilateral triangle, which is circumscribed by a circle, which is circumscribed by a square, which is circumscribed by yet another circle, and so forth.
Answer two questions:
1. What is the radius of the outermost circle?
2. Is finding the value of this radius an exercise/problem in discrete mathematics or continuous mathematics?

Thank you!

Found 2 solutions by rothauserc, ikleyn:
Answer by rothauserc(4718) About Me  (Show Source):
You can put this solution on YOUR website!
This is a problem in discrete mathematics, consider the definition of a circle in discrete mathematics
:
the circle is comprised of polygons of n sides as n approaches infinity
:
begin with the circle of radius 1 inscribed in the equilateral triangle
:
the radius of the next circle is 1 / sin 30 = 2
:
the interior angle of regular polygon is (n-2)180/n
:
the hypotenuse (radius of the next circle) = radius of previous circle / the sin of (interior angle / 2)
:
the radius of the next circle is 2 / sin 45 = 2.828427125
:
the radius of the next circle is 2.828427125 / sin 54 = 3.496128196
:
the radius of the next circle is 3.496128196 / sin 60 = 4.03698111
:
the radius of the next circle is 4.03698111 / sin 64.28 = 4.480926229
:
the radius of the next circle is 4.480926229 / sin 67.5 = 4.8501196
:
the radius of the next circle is 4.8501196 / sin 70 = 5.161389472
:
now we look for the limit of this sequence
:
**************************************************************************
The limit of this sequence is "Polygon Circumscribing Constant" which is defined as
:
limit for n > = 3 of the product of 1 / cos(pi/n) = 8.7000366
**************************************************************************
:

Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.
There is even more simple formula

R%5Bn%2B1%5D = R%5Bn%5D%2Fcos%28pi%2Fn%29.      (1)

The table below is obtained from Excel, formula (1).

n	cos%28pi%2Fn%29	R%5Bn%5D
1	-	-
2	-	-
3	0.500000	1.000000
4	0.707107	2.000000
5	0.809017	2.828427
6	0.866025	3.496128
7	0.900969	4.036981
8	0.923880	4.480711
9	0.939693	4.849887
10	0.951057	5.161142
11	0.959493	5.426745
12	0.965926	5.655847
13	0.970942	5.855364
14	0.974928	6.030602
15	0.978148	6.185690
16	0.980785	6.323882
17	0.982973	6.447774
18	0.984808	6.559462
19	0.986361	6.660652
20	0.987688	6.752751
21	0.988831	6.836924
22	0.989821	6.914150
23	0.990686	6.985249
24	0.991445	7.050922
25	0.992115	7.111764
26	0.992709	7.168288
27	0.993238	7.220937
28	0.993712	7.270095
29	0.994138	7.316097
30	0.994522	7.359237
31	0.994869	7.399774
32	0.995185	7.437936
33	0.995472	7.473925
34	0.995734	7.507921
35	0.995974	7.540086
36	0.996195	7.570563
37	0.996397	7.599481
38	0.996584	7.626957
39	0.996757	7.653096
40	0.996917	7.677994

Some info about this sequence see in the page https://oeis.org/A051762.