góc AOD=góc BOC=600(đối đỉnh)
góc AOC+góc BOC=1800
=> góc AOC+600=1800
=> góc AOC=1200
=> góc BOD=góc AOC=1200 (đối đỉnh)
Ta có: \(\widehat{BOC}+\widehat{BOD}=180^o\) (kề bù)
\(60^o+\widehat{BOD}=180^o\)
\(\widehat{BOD}=120^o\)
Ta có : \(\widehat{BOC}=\widehat{AOD}=60^o\) ( đối đỉnh)
\(\widehat{BOD}=\widehat{AOC}=120^o\) ( đối đỉnh)
\(\widehat{AOD}=\widehat{BOC}=60^0\)
\(\widehat{AOC}=\widehat{BOD}=180^0-60^0=120^0\)