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similar triangles with integer sides, and 2 equal sides

Source: Netherlands - Dutch NMO 1968 p3

February 1, 2023
geometrysimilar triangles

Problem Statement

ABCABC\vartriangle ABC \sim \vartriangle A'B'C'. ABC\vartriangle ABC has sides a,b,ca,b,c and ABC\vartriangle A'B'C' has sides a,b,ca',b',c'. Two sides of ABC\vartriangle ABC are equal to sides of ABC\vartriangle A'B'C'. Furthermore, a<aa < a', a<b<ca < b < c, a=8a = 8. Prove that there is exactly one pair of such triangles with all sides integers.