MathDB
Point of concurrence on the altitude

Source: Iberoamerican 2015 #4

November 11, 2015
geometry

Problem Statement

Let ABCABC be an acute triangle and let DD be the foot of the perpendicular from AA to side BCBC. Let PP be a point on segment ADAD. Lines BPBP and CPCP intersect sides ACAC and ABAB at EE and FF, respectively. Let JJ and KK be the feet of the peroendiculars from EE and FF to ADAD, respectively. Show that
FKKD=EJJD\frac{FK}{KD}=\frac{EJ}{JD}.