MathDB
<AA_ K=<BB_1M when B_1K//BC, A_1M//AC (Kharkiv City XI 2013 - Ukr)

Source:

March 13, 2020
geometryparallelequal anglesanglesKharkiv

Problem Statement

In the triangle ABCABC, the heights AA1AA_1 and BB1BB_1 are drawn. On the side ABAB, points MM and KK are chosen so that B1K∥BCB_1K\parallel BC and A1M∥ACA_1 M\parallel AC. Prove that the angle AA1KAA_1K is equal to the angle BB1MBB_1M.
Back to ProblemsView on AoPS