MathDB
Estonian Math Competitions 2006/2007

Source: Juniors Problem 2

July 29, 2008
calculusintegrationratiogeometryperimeternumber theory unsolvednumber theory

Problem Statement

Call a scalene triangle K disguisable if there exists a triangle K′ similar to K with two shorter sides precisely as long as the two longer sides of K, respectively. Call a disguisable triangle integral if the lengths of all its sides are integers. (a) Find the side lengths of the integral disguisable triangle with the smallest possible perimeter. (b) Let K be an arbitrary integral disguisable triangle for which no smaller integral disguisable triangle similar to it exists. Prove that at least two side lengths of K are perfect squares.