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Inequality between the lengths of the sides of a triangle

Source: Poland Math Olympiad 1993 Round 1 #3

June 3, 2023
inequalities

Problem Statement

Prove that if a,b,ca,b,c are the lengths of the sides of a triangle, then 1a+1b+1c1a+bc+1c+ab+1b+ca\frac{1}{a}+\frac{1}{b}+\frac{1}{c} \leq \frac{1}{a+b-c}+\frac{1}{c+a-b}+\frac{1}{b+c-a}.