Problem

Source: Indonesia IMO 2010 TST, Stage 1, Test 1, Problem 4

Tags: trigonometry, geometry, geometric transformation, reflection, circumcircle, angle bisector, similar triangles



Let $ ABC$ be a non-obtuse triangle with $ CH$ and $ CM$ are the altitude and median, respectively. The angle bisector of $ \angle BAC$ intersects $ CH$ and $ CM$ at $ P$ and $ Q$, respectively. Assume that \[ \angle ABP=\angle PBQ=\angle QBC,\] (a) prove that $ ABC$ is a right-angled triangle, and (b) calculate $ \dfrac{BP}{CH}$. Soewono, Bandung