(1)∠MON=∠MOC-∠NOC=(∠AOC-∠AOM)-(∠BOC-∠BON)∵∠AOC=∠AOB+∠BOC=150° ∠BOC=60°∴∠AOM=50° ∠BON=20°∴∠MON=60°(2)∠MON=∠MOC-∠NOC=(∠AOC-∠AOM)-(∠BOC-∠BON)=(2/3)∠AOC-40°=(2/3)(α+60°)-40°=(2/3)α(3)∠MON=∠MOC-∠NOC=(∠AOC-∠AOM)-(∠BOC-∠BON)=(2/3)(∠AOC-∠BOC)