Question

AB,AC为圆o的弦,连接CO,BO并延长分别交弦AB,AC于点E,F∠B=∠C求证AB=AC

Answer 1

∵OA＝OB＝OC,∴∠OAB＝∠OBA、∠OAC＝∠OCA,而∠OBA＝∠OCA,

∴∠OAB＝∠OAC,又∠OBA＝∠OCA、OB＝OC,∴△OAB≌△OAC,∴AB＝AC.