a) \(\widehat{AOB}=\widehat{AOM}+\widehat{MOB}\)
\(\Rightarrow\widehat{MOB}=\widehat{AOB}-\widehat{AOM}\)
mà \(\widehat{AOM}=90^o\) (OM vuông góc OA)
\(\Rightarrow\widehat{MOB}=100^o-90^o\)
\(\Rightarrow\widehat{MOB}=10^o\)
Câu b bạn xem lại đề
b) \(\widehat{B'OA}+\widehat{AOB}=180^o\) (2 góc kề bù)
\(\Rightarrow\widehat{B'OA}=180^o-\widehat{AOB}\)
\(\Rightarrow\widehat{B'OA}=180^o-100^o\)
\(\Rightarrow\widehat{B'OA}=80^o\)
\(\widehat{MOB'}=\widehat{B'OA}+\widehat{AOM}\)
\(\Rightarrow\widehat{MOB'}=80^o+90^o\)
\(\Rightarrow\widehat{MOB'}=170^o\)
b,gọi OB' là tia đối của tia OB.Tính góc MOB'