MathDB
anglechasing with incenter, 60^o wanted (Singapore Junior 2006)

Source:

July 10, 2019
geometryAngle Chasingangle bisectorincenter

Problem Statement

In ABC\vartriangle ABC, the bisector of B\angle B meets ACAC at DD and the bisector of C\angle C meets ABAB at EE. These bisectors intersect at OO and OD=OEOD = OE. If ADAEAD \ne AE, prove that A=60o\angle A = 60^o.