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possible triangle inequality
sunshine_12   2
N Mar 31, 2025 by sunshine_12
a, b, c are real numbers
|a| + |b| + |c| − |a + b| − |b + c| − |c + a| + |a + b + c| ≥ 0
hey everyone, so I came across this inequality, and I did make some progress:
Let (a+b), (b+c), (c+a) be three sums T1, T2 and T3. As there are 3 sums, but they can be of only 2 signs, by pigeon hole principle, atleast 2 of the 3 sums must be of the same sign.
But I'm getting stuck on the case work. Can anyone help?
Thnx a lot
2 replies
sunshine_12
Mar 30, 2025
sunshine_12
Mar 31, 2025
possible triangle inequality
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sunshine_12
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a, b, c are real numbers
|a| + |b| + |c| − |a + b| − |b + c| − |c + a| + |a + b + c| ≥ 0
hey everyone, so I came across this inequality, and I did make some progress:
Let (a+b), (b+c), (c+a) be three sums T1, T2 and T3. As there are 3 sums, but they can be of only 2 signs, by pigeon hole principle, atleast 2 of the 3 sums must be of the same sign.
But I'm getting stuck on the case work. Can anyone help?
Thnx a lot
This post has been edited 2 times. Last edited by sunshine_12, Mar 30, 2025, 2:41 PM
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kiyoras_2001
666 posts
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Hlawka's inequality
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sunshine_12
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thank u so much for the reference but i'm wondering abt the solution using pigeonhole principle. if u have any insights or ideas on how to proceed with that, i'd really appreciate it.
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