Vì là hai góc kề bù \(\Rightarrow\widehat{AOB}+\widehat{BOC}=180^o\)
Mà \(\widehat{AOB}=\dfrac{2}{3}\widehat{BOC}\)
\(\Rightarrow\dfrac{2}{3}\widehat{BOC}+\widehat{BOC}=180^o\)
\(\Rightarrow\dfrac{5}{3}\widehat{BOC}=180^o\)
\(\Rightarrow BOC=180^o\div\dfrac{5}{3}=108^o\)
Mà : \(\widehat{AOB}+\widehat{BOC}=180^o\)
\(\Rightarrow\widehat{AOB}+108^o=180^o\Rightarrow\widehat{AOB}=72^o\)
Vậy ...
Bài này k vẽ hình nhé
Vì \(AOB\) và \(BOC\) là 2 góc kề bù nên
\(AOB+BOC=180^0.\) mÀ \(AOB=\dfrac{2}{3}BOC\) nên \(\dfrac{2}{3}BOC+BOC=180^0\)
\(BOC.\left(\dfrac{2}{3}+1\right)=180^0\)
\(BOC.\dfrac{5}{3}=180^0\)
\(BOC=180^0:\dfrac{5}{3}=180.\dfrac{3}{5}\)
\(BOC=108^0\)
Vậy \(AOB=\dfrac{2}{3}BOC=\dfrac{2}{3}.108^0=72^0\)
\(AOB=72^0\)
