摘要：4．如图2 ∠AOC= + = - ∠AOD-∠AOB = = + , ∠BOC= - - - =∠AOC - = - ∠COD
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25、如图，OC是∠AOB的平分线，且∠AOD=90°．
10、如图，（1）∠AOC=∠AOB
+∠BOC
=∠AOD
-∠COD
；（2）∠AOD-∠AOB=
∠BOD
=∠BOC
+∠COD
；（3）∠BOC=
∠AOD
-∠AOB
-∠COD
=∠AOC-∠AOB
=∠BOD
-∠COD．
如图，∠AOB=∠COD=90°，OE平分∠AOC，∠AOD=120°．
如图，∠AOB=90°，∠COD=90°，∠AOC=35°．