Let P be a point strictly in the interior of a scalene triangle A B C with integer side lengths, and let
f ( P ) = P A + P B + P C
For each triangle A B C , let h A B C = min P [ f ( P ) ] .
Now, consider all triangles for which P A , P B , P C are all integers. The first smallest value minimum value of h A B C = Q 1 = 1 6 4 6 4 for which exist two integer triangles with equal sum of integer Torricheli-Ferma distanses
P A 1 1 + P B 1 1 + P C 1 1 = P A 1 2 + P B 1 2 + P C 1 2 = 1 6 4 6 4 P A 1 1 = 6 8 2 5 , P B 1 1 = 5 5 4 4 , P C 1 1 = 4 0 9 5 P A 1 2 = 7 0 4 0 , P B 1 2 = 5 2 0 0 , P C 1 2 = 4 2 2 4
What is the next (second) value of equal sum h A B C = Q 2 that there exist two triangles
P A 2 1 + P B 2 1 + P C 2 1 = P A 2 2 + P B 2 2 + P C 2 2 = Q 2 ?
Use a computer for your calculation. This problem is connect with P and that next triangle .
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Since a Torricelli-Fermat point P has the property that ∠ A P B = ∠ A P C = ∠ B P C = 1 2 0 ° , then by the law of cosines:
A B 2 = P A 2 + P B 2 − 2 ⋅ P A ⋅ P B ⋅ cos 1 2 0 ° = P A 2 + P A ⋅ P B + P B 2
A C 2 = P A 2 + P C 2 − 2 ⋅ P A ⋅ P C ⋅ cos 1 2 0 ° = P A 2 + P A ⋅ P C + P C 2
B C 2 = P B 2 + P C 2 − 2 ⋅ P B ⋅ P C ⋅ cos 1 2 0 ° = P B 2 + P B ⋅ P C + P C 2
The below Python program finds all numbers a and b between 0 < a < b < 1 5 0 0 0 such that a 2 + a b + b 2 is a perfect square, then uses that list to find integer sets of ( P A , P B , P C ) that give integer triangle sides, and finally displays all h = P A + P B + P C with more than one possible ( P A , P B , P C ) set. The second h value computes to 2 0 2 8 0 .