The triangle with edge lengths 3, 4, and 5 is the right triangle with smallest possible integer lengths and corresponds to the Pythagorean triple where the legs have lengths 3 and 4 and the hypotenuse length 5. It satisfies the Pythagorean theorem since
(1)
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It has inradius
(2)
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Triangle line picking for points picked at random in a 3, 4, 5 triangle gives a mean line segment length of
(3)
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(4)
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(E. W. Weisstein, Aug. 6-9, 2010; OEIS A180307).