MathDB
BMT 2021 Geometry Tiebreaker #2

Source:

August 12, 2023
geometry

Problem Statement

Let A0B0C0\vartriangle A_0B_0C_0 be an equilateral triangle with area 11, and let A1A_1, B1B_1, C1C_1 be the midpoints of A0B0\overline{A_0B_0}, B0C0\overline{B_0C_0}, and C0A0\overline{C_0A_0}, respectively. Furthermore, set A2A_2, B2B_2, C2C_2 as the midpoints of segments A0A1\overline{A_0A_1}, B0B1\overline{B_0B_1}, and C0C1\overline{C_0C_1} respectively. For n1n \ge 1, A2n+1A_{2n+1} is recursively defined as the midpoint of A2nA2n1A_{2n}A_{2n-1}, and A2n+2A_{2n+2} is recursively defined as the midpoint of A2n+1A2n1\overline{A_{2n+1}A_{2n-1}}. Recursively define BnB_n and CnC_n the same way. Compute the value of limn[AnBnCn]\lim_{n \to \infty }[A_nB_nC_n], where [AnBnCn][A_nB_nC_n] denotes the area of triangle AnBnCn\vartriangle A_nB_nC_n.