1.∠EOB=1/2∠COF+1/2∠FOA=1/2COA=(180-100)/2=40
2.會(huì)變化 ∠ofc=∠foa=2∠boa ∠ofc=2∠obc 當(dāng)AB在co左邊時(shí),∠ofc=50,則∠obc=25當(dāng)AB在co右邊時(shí)∠ofc=40 ∠obc=20
3.可能,因?yàn)槠叫?則∠OEC=∠EOA ∠OBA=∠COB 若∠OEC=∠OBA,則∠COE=∠AOB.又因?yàn)椤螰OB=∠AOB,∠COE=∠EOF.則2∠COE=2∠AOB=40 ∠COE=∠AOB=20 則∠OEC=∠OBA=∠COE＋∠EOB=60