Maths Olympiad Prep

Track / Stage 7 / 1 of 300 #1401 of 1964

Problem 1401

National Olympiad second round; IMO P1/P4
Geometry Difficulty 7.0 Prove it BMO Round 1 · United Kingdom · 2008

Let ABCABC be a triangle, with an obtuse angle at AA. Let QQ be a point (other than AA, BB or CC) on the circumcircle of the triangle, on the same side of chord BCBC as AA, and let PP be the other end of the diameter through QQ. Let VV and WW be the feet of the perpendiculars from QQ onto CACA and ABAB respectively. Prove that the triangles PBCPBC and AWVAWV are similar. [Note: the circumcircle of the triangle ABCABC is the circle which passes through the vertices AA, BB and CC.]

This one wants a proof. Work it on paper, then check yourself against the publisher's own solution, linked below. Be honest about it: the record is only any use to you if it is.

Next problem →

We don't reproduce this publisher's solutions. Their own solution is here — work the problem first.

Source: UK Mathematics Trust, licensed © UK Mathematics Trust; question papers published free at bmos.ukmt.org.uk. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project. Solutions are the publisher's, linked not copied.