MathDB
Diameter of Circumcircle

Source: 1992 IrMO Paper 1 Problem 4

October 2, 2017
geometrycircumcircle

Problem Statement

In a triangle ABCABC, the points AA’, BB’ and CC’ on the sides opposite AA ,BB and CC, respectively, are such that the lines AAAA’, BBBB’ and CCCC’ are concurrent. Prove that the diameter of the circumscribed circle of the triangle ABCABC equals the product ABBCCA|AB’|\cdot |BC’|\cdot |CA’| divided by the area of the triangle ABCA’B’C’.