Question

如下图：已知：∠AOB＝60°,OD、OE分别是∠BOC和∠COA的平分线.（1）如图1,OC在∠AOB内部时,求∠DO

Answer 1

1 ∠AOB=60°

∠DOC=1/2∠BOC

∠EOC=1/2∠AOC

∠DOE=∠DOC+∠EOC=1/2∠BOC+1/2∠AOC=1/2∠AOB=30°

2 ∠DOC=1/2∠BOC

∠EOC=∠AOE=1/2∠AOC

∠DOE=∠COE-∠DOC=1/2∠AOB=30°

3 30°