(OB bisect. ∠AOC, ∠BOC=20° ⇒ ∠AOC=2∠BOC=40°.
(OC bisect. ∠AOD, ∠AOC=40° ⇒ ∠COD=∠AOC=40°
(OD bisect. ∠BOE, ∠BOD=∠BOC+∠COD=60°, dar (OD fiind bisect. ⇒ ∠BOD=∠DOE=60°.