GeometryDifficulty 7.0Prove itBMO Round 1 · United Kingdom · 2008
Let ABC be a triangle, with an obtuse angle at A. Let Q be a point (other than A, B or C) on the circumcircle of the triangle, on the same side of chord BC as A, and let P be the other end of the diameter through Q. Let V and W be the feet of the perpendiculars from Q onto CA and AB respectively. Prove that the triangles PBC and AWV are similar. [Note: the circumcircle of the triangle ABC is the circle which passes through the vertices A, B and C.]
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.