MathDB
Bisector and altitude relations

Source: Turkey TST 2019 Day 1 P3

March 26, 2019
geometry

Problem Statement

In a triangle ABCABC, AB>ACAB>AC. The foot of the altitude from AA to BCBC is DD, the intersection of bisector of BB and ADAD is KK, the foot of the altitude from BB to CKCK is MM and let BMBM and AKAK intersect at point NN. The line through NN parallel to DMDM intersects ACAC at TT. Prove that BMBM is the bisector of angle TBC^\widehat{TBC}.