Làm bài 4, nhanh= ctrlhn+5*+cm

Ta có:

`\hat{AOC}+\hat{COB}=180^o(\text{kề bù})`

Mà `\hat{AOC}=5\hat{COB}`

`=>5\hat{COB}+\hat{COB}=180^o`

`=>\hat{COB}=30^o`

`=>\hat{AOC}=5.30^o=150^o`

`=>`

`\hat{AOD}=\hat{COB}=30^o(\text{đối đỉnh})`

`\hat{BOD}=\hat{AOC}=150^o(\text{đối đỉnh})`

`\text{___________________________________}`

Đáp án:

`\hat{AOD}=\hat{COB}=30^o`

`\hat{BOD}=\hat{AOC}=150^o`