∡AOB; ∡BOC-∡adiacente, suplementare
⇒m(∡AOB)+m(∡BOC)=180°
m(∡AOB)=60°⇒m(∡BOC)=180°-60°=120°
[OE-bis ∡BOC⇒m(∡COE)=m(∡BOE)=120°/2=60°
[OD-opusa cu [OB⇒m(∡BOD)=180°
m(∡COD)=180°-m(∡BOC)=180°-120°=60°
m(∡DOF)=90°-60°=30°
m(∡EOF)=m(∡COE)+m(∡COF)=60°+90°=150°
