MathDB
incenter wanted , <BIC = < IDC, cyclic ABCD

Source: 2008 Indonesia TST stage 2 test 3 p1

December 14, 2020
geometryincentercyclic quadrilateral

Problem Statement

Let ABCDABCD be a cyclic quadrilateral, and angle bisectors of ∠BAD\angle BAD and ∠BCD\angle BCD meet at point II. Show that if ∠BIC=∠IDC\angle BIC = \angle IDC, then II is the incenter of triangle ABDABD.
Back to ProblemsView on AoPS