MathDB
nice geometry

Source: 2016 KJMO #6

November 13, 2016
geometry

Problem Statement

circle O1O_1 is tangent to ACAC, BCBC(side of triangle ABCABC) at point D,ED, E. circle O2O_2 include O1O_1, is tangent to BCBC, ABAB(side of triangle ABCABC) at point E,FE, F The tangent of O2O_2 at P(DEO2,PE)P(DE \cap O_2, P \neq E) meets ABAB at QQ. A line passing through O1O_1(center of O1O_1) and parallel to BO2BO_2(O2O_2 is also center of O2O_2) meets BCBC at GG, EQAC=K,KGEF=LEQ \cap AC=K, KG \cap EF=L, EO2EO_2 meets circle O2O_2 at N(E)N(\neq E), LO2FN=MLO_2 \cap FN=M. IF NN is a middle point of FMFM, prove that BG=2EGBG=2EG