(1)∵OB是∠AOC的角平分线, 则∠AOC=∠AOB+∠BOC; ∠BOD=∠BOC+∠COD; ∠DOE=∠COE-∠COD; ∠AOB=∠AOC-∠BOC; ∠DOE=∠AOE-∠AOD;
(2)OB是∠AOC的角平分线,OD是∠COE的角平分线, ∠BOD=∠AOB+∠DOE=40°+30°=70°;
(3)∵OD是∠COE的角平分线, ∠COD=∠DOE=30°, ∠AOC=∠AOE-∠COE=140°-30°-30°=80°, OB是∠AOC的角平分线,∠AOB=∠BOC, ∠AOB=∠AOC=40°. |