MathDB
Interesting geometry

Source:

May 20, 2018
geometrytrigonometrybashIsicmi

Problem Statement

Let ABCABC be an equilateral triangle of side length 22. Point AA' is chosen on side BCBC such that the length of ABA'B is k<1k<1. Likewise points BB' and CC' are chosen on sides CACA and ABAB. with CB=AC=kCB'=AC'=k. Line segments are drawn from points A,B,CA',B',C' to their corresponding opposite vertices. The intersections of these line segments form a triangle, labeled PQRPQR. Prove that ΔPQR\Delta PQR is an equilateral triangle with side length 4(1k)k22k+4{4(1-k) \over \sqrt{k^2-2k+4}}.