#proofing with pigeonhole principle

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royal mangoBOT
median cairn
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<@&286206848099549185>

wary plank
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@median cairn Sometimes, the problem gives you the bare minimum. Why 10 points in particular? Can you place 9 points into a square such that no two points are closer than 0.48 units?

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I will say, splitting the square into smaller squares is the correct approach.

median cairn
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hmm im not sure if 9 would work because the sidelengths would be too small for it to be 0.48 units apart

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since itd all be 0.11 i think

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per smaller square

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the proof i wrote right now splits the square into 4 smaller squares of 0.5 length but then uses the general pigeonhole principle, since there will eventually be 2 or more points in the same space within 0.50, so those two are within 0.48 then

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if theyre within 0.50

wary plank
# median cairn if theyre within 0.50

That would not necessarily follow. If you have 2 points in a square of side length 0.5, then simply place them at two corners and they are 0.5 apart from each other.

wary plank
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I don't think splitting into four squares will work. If you have 2 vertices in a square of side length 0.5, you cannot conclude that those points are less than 0.48 units apart. No can you do anything if you have 4 points in a square of side length 0.5.

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The general pigeon-hole principle does say that 3 points will be in the same square of side length 0.5, but I don't think you can do anything from that.

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Here, splitting the square into 4 squares does not help at all.

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Primarily because you are forced to focus on pairs of distant points, or a trio of distant points.

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And you cannot see the cluster of 4 points obviously close to each other.

median cairn
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If i do 9 wont each side have to be 0.333?

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For it to all add up to 1? Rhat was my main concern

wary plank
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Yes. Each square will have side length 1/3.

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Now, what does the pigeon-hole principle tell you?

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@median cairn

median cairn
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If theres n > k compartments

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Then one will have more than 1

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So 1 will have 2

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Ahhh i see now

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Thank you

wary plank
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Once you do the math, you'll see why there is a 0.48.

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Good luck

median cairn
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i see now, i calculated the really precise value of the side length if you split it into thirds to satisfy the 0.48 condition

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and also since it is 0.48 in diagonal distance then even if the points are placed at each corner