Ta có: `hat{AOC} = hat{BOD}` (2 góc đối đỉnh)
`hat{AOC} + hat{BOD} = 140^o` (gt)
`=> hat{AOC} = hat{BOD} = 140^o/2 = 70^o`
Lại có: `hat{AOD} + hat{AOC} = 180^o` (2 góc kề bù)
`=> hat{AOD} = 180^o - hat{AOC} = 180^o - 70^o = 110^o`
Mà `hat{AOD} = hat{BOC}` (2 góc đối đỉnh)
`=> hat{AOD} = hat{BOC} = 110^o`
Ta có: \(\widehat{AOC}=\widehat{BOD}\)(hai góc đối đỉnh)
mà \(\widehat{AOC}+\widehat{BOD}=140^0\)
nên \(\widehat{AOC}=\widehat{BOD}=\dfrac{140^0}{2}=70^0\)
Vậy: \(\widehat{AOC}=70^0;\widehat{BOD}=70^0;\widehat{DOA}=110^0;\widehat{BOC}=110^0\)