∠AOB=180°
∠DOC=∠AOD
∠BOE=2∠COE
∠DOC+∠COE=∠DOE=72°
∠AOD+∠COE=72°
∠AOD+∠DOC+2∠COE=72×2=144°
∠AOB-(∠AOC+∠BOE)=∠COE
180-144=36°(∠COE)
2×36=72°(∠BOE)
∠AOB=180°
∠DOC=∠AOD
∠BOE=2∠COE
∠DOC+∠COE=∠DOE=72°
∠AOD+∠COE=72°
∠AOD+∠DOC+2∠COE=72×2=144°
∠AOB-(∠AOC+∠BOE)=∠COE
180-144=36°(∠COE)
2×36=72°(∠BOE)