a/
\(\widehat{xOt}=\widehat{tOy}=\dfrac{\widehat{xOy}}{2}=\dfrac{60^o}{2}=30^o\)
b/
\(\widehat{xAm}=\widehat{xOy}=60^o\)
Hai góc trên ở vị trí đồng vị => Am//Oy
c/
Ta có
Am//Oy (cmt) \(\Rightarrow\widehat{ACO}=\widehat{tOy}\) (góc so le trong)
BC//Ox (gt) \(\Rightarrow\widehat{BCO}=\widehat{xOt}\) (góc so le trong)
Mà \(\widehat{xOt}=\widehat{tOy}\left(cmt\right)\)
\(\Rightarrow\widehat{ACO}=\widehat{BCO}\)