MathDB
concurrent lines

Source: Ireland 1996

July 1, 2009
geometrycircumcirclegeometry unsolved

Problem Statement

In an acute-angled triangle ABC ABC, D,E,F D,E,F are the feet of the altitudes from A,B,C A,B,C, respectively, and P,Q,R P,Q,R are the feet of the perpendiculars from A,B,C A,B,C onto EF,FD,DE EF,FD,DE, respectively. Prove that the lines AP,BQ,CR AP,BQ,CR are concurrent.
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