Points $A_1$, $B_1$, $C_1$ are midpoints of sides $BC$, $AC$, $AB$ of triangle $ABC$. On midlines $C_1B_1$ and $A_1B_1$ points $E$ and $F$ are chosen such that $BE$ is the angle bisector of $AEB_1$ and $BF$ is the angle bisector of $CFB_1$. Prove that bisectors of angles $ABC$ and $FBE$ coincide. Proposed by F. Baharev
Problem
Source: St. Petersburg MO 2001, 9th grade, P5
Tags: geometry, isogonal conjugates, midline, isogonal lines, sine chasing, angle bisector