IMO 1985 LL SWE77
Two equilateral triangles are inscribed in a circle with radius
IMO 1985 LL SWE77
Origin: SWE
Problem
Two equilateral triangles are inscribed in a circle with radius r. Let A be the area of the set consisting of all points interior to both triangles. Prove that 2A \geqr2\sqrt 3.