Infinitely many tangent circles cover the plane in a repeating pattern as per graphic showing some of them.
Let x be the fraction of the plane the circles cover.
Evaluate ⌊ 1 0 0 0 x ⌋ .
Note : There are just 5 different circle radii, corresponding to circles (from smallest to largest) that are tangent to 4, 5, 6, 7, 8 other circles. 14 of these circles can form a pattern that "tiles the plane".
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You can delete all my conversations here because they are all irrelevant to this question. Just hope that this question can become more complete so that misunderstanding like me may not happen again. I was totally out of this question!
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There's nothing wrong with rechecking my own work. What had happened was that when I went over my equations over again, I decided to make a slight change in the variables, so that a , b , c , d would be in order of size. I made a slight mistake in doing so, and consequently I had gotten almost exactly the same result you did! I went over them again and cleared up the mistake, and then decided I better post the solution here to prevent any further misunderstandings.
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Don't worry. It was just that I didn't answer to the question. However, a near approximation is not too surprising because the figures ought to be around there. I think this question can be solved by me now. Hope that this question shall get best appearance in Brilliant and liked by solvers. All the best!
Shocked in the first place that I don't think I would have proven this even if plenty more of time is given to me. I was right to surrender to this question. Let me see how you can make it in this way.
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Well, you made me look at my equations twice!
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I thought you were just kidding. How could you got a shaken of mind with 934? In fact, the second diagram has not given me an obvious reason to be logical.
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@Lu Chee Ket – I'm not sure what your point is, so correct me if I'm wrong.
Maybe the question can be clearer if it states that by connecting the big circle's centers together we could form a square.
Other than that, I am sure there exists only 1 solution .
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@Julian Poon – I only need to see the word "pattern". You can justify how I thought that the circles are totally random. Forgive me for disturbing. Thanks!
@Julian Poon – Thank you very much for the special tool that I may be able to apply. You can become very strong with the tool onto questions like this one. I hope I can also be stronger at these questions.
@Julian Poon – I'm glad you mentioned about this being the "only 1 solution". It's a very interesting tessellation of the plane. I first noticed it a while back when I came across some Islamic Art, but now I can't seem to find it.
Did you add in the "Note"? I didn't notice that there were just 5 different radii. I thought that you simply have any circles combined. I was totally out of the question. There are smallest circles which do not seem like making the infinite structure congruent.
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The note was added at least 1.5 hours ago.
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I see. I was not answering to the question. Thanks!
The smallest circles should be more complete to appear at some other places, otherwise the orientation of the diagram ought to be more obvious and sincere at least. This made an innocent trick to me. I suggest that the question ask a straight forward challenge. It was a trick rather than difficult. I don't know how I didn't read the description of Note.
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Right triangle Δ A B C shows the geometrical relation between all 5 circles, the radii being 1 , a , b , c , d from smallest to largest. The following relations must hold
c = 1 + 2
1 + c + ( b + c ) 2 − b 2 = 2 b + d
2 ( 2 b + d ) = 2 1 ( 1 + c ) + ( a + c ) 2 − c 2 + a + d
( a + d ) 2 + ( b + d ) 2 − 2 ( a + d ) ( b + d ) C o s ( 4 5 ) = a + b
which numerically leads to
a = 1 . 7 0 1 8 0 0 …
b = 2 . 1 8 0 1 4 9 …
c = 2 . 4 1 4 2 3 5 …
d = 3 . 0 9 8 0 6 1 …
The area of the triangle, the circles inside the triangle, and the ratio are
Δ A B C = 2 1 ( 2 b + d ) 2 = 2 7 . 8 1 3 5 9 9 . . .
Circles = 2 1 π ( a 2 + b 2 + c 2 ) + 8 1 π ( 1 + d 2 ) = 2 5 . 3 3 2 3 7 8 . . .
Ratio = 0 . 9 1 0 7 9 2 …
Here's a sketch copy of the original Islamic artwork (which I can't find now) that suggested this problem