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Area ratios

Source: APMO 1989

March 10, 2006
geometryratioLaTeXanalytic geometrysimilar trianglesgeometry unsolved

Problem Statement

Let A1A_1, A2A_2, A3A_3 be three points in the plane, and for convenience, let A4=A1A_4= A_1, A5=A2A_5 = A_2. For n=1n = 1, 22, and 33, suppose that BnB_n is the midpoint of AnAn+1A_n A_{n+1}, and suppose that CnC_n is the midpoint of AnBnA_n B_n. Suppose that AnCn+1A_n C_{n+1} and BnAn+2B_n A_{n+2} meet at DnD_n, and that AnBn+1A_n B_{n+1} and CnAn+2C_n A_{n+2} meet at EnE_n. Calculate the ratio of the area of triangle D1D2D3D_1 D_2 D_3 to the area of triangle E1E2E3E_1 E_2 E_3.