n concurrent lines given - All-Russian MO 2003 Regional (R4) 10.4
Source:
September 17, 2024
geometrycombinatoricscombinatorial geometry
Problem Statement
On the plane we mark () straight lines passing through one point in such a way that for any two of them there is a marked straight line that bisects one of the pairs of vertical angles, formed by these straight lines. Prove that the drawn straight lines divide full angle into equal parts.