IMO 1989 LL VIE107

Let E be the set of all triangles whose only points with integer

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IMO 1989 LL VIE107

Origin: VIE

Problem

Let E be the set of all triangles whose only points with integer coordinates (in the Cartesian coordinate system in space), in its interior or on its sides, are its three vertices, and let f be the function of area of a triangle. Determine the set of values f(E) of f.