MathDB
Prove CD^2=BDxCE

Source: China Second Round 2015 (B) Q2

May 5, 2016
geometryincenter

Problem Statement

In isoceles ABC\triangle ABC, AB=ACAB=AC, II is its incenter, DD is a point inside ABC\triangle ABC such that I,B,C,DI,B,C,D are concyclic. The line through CC parallel to BDBD meets ADAD at EE. Prove that CD2=BDCECD^2=BD\cdot CE.