có \(\widehat{AOC}+\widehat{COD}+\widehat{DOB}=\widehat{AOB}\)
\(hay\widehat{AOC}+70^o+\widehat{DOB}=180^o\)
\(\Rightarrow\widehat{AOC}+\widehat{DOB}=180^o-70^o\)
\(\Rightarrow\widehat{AOC}+\widehat{DOB}=110^o\)
\(\Rightarrow\widehat{AOC}=\left(110^o+10^o\right)\div2\)
\(\Rightarrow\widehat{AOC}=60^o\)
có \(\widehat{AOC}-\widehat{DOB}=10^o\)
\(hay60^o-\widehat{DOB}=10^o\)
\(\Rightarrow\widehat{DOB}=60^o-10^o\)
\(\Rightarrow\widehat{DOB}=50^o\)
Giải thích giùm mình tại sao AOC + COD + DOB = AOB
do \(\widehat{AOC}+\widehat{COD}=\widehat{AOD}\)
mà\(\widehat{AOD}+\widehat{DOB}=\widehat{AOB}\)
\(\Rightarrow\widehat{AOC}+\widehat{COD}+\widehat{DOB}=\widehat{AOB}\)