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MathNet 2021 — Part 06 Question 93

Math Olympiad Vault · MathNet 2021 — Part 06

Question 93

Suppose $a$, $b$, $c$ are the side lengths of a triangle $ABC$ with area $S$, and semi-perimeter $s$. Prove that
$$
s \lt \sqrt{a^2 + b^2 - 4S} + \sqrt{b^2 + c^2 - 4S} + \sqrt{c^2 + a^2 - 4S}.
$$