2。 55' 18' 145' 18'

3.∠4 ∠4 and ∠ 1

∠AOE ∠BOD and∠ ∠AOD are complementary.

4.( 1): 35'

(2): 120'

5: (1) ∠COB is 60' ∠BOD is 30' ∠AOD is 120' (2) ∠ COB, because ∠BOD and ∠COB are redundant.

6: AOB and ∠COB. Because OC is the bisector of ∠BOD, then OB is also the bisector of ∠AOC, so ∠AOB and ∠COB are complementary.