Problem

Source: China TST 1998, problem 4

Tags: geometry, circumcircle, incenter, trigonometry, geometry unsolved



In acute-angled $\bigtriangleup ABC$, $H$ is the orthocenter, $O$ is the circumcenter and $I$ is the incenter. Given that $\angle C > \angle B > \angle A$, prove that $I$ lies within $\bigtriangleup BOH$.