a) $\widehat{OEA}=\widehat{OAE}$;$\widehat{O'AF}=\widehat{O'FA}$mà $\widehat{OAE}=\widehat{O'AF}$$\Rightarrow \widehat{OEA}=\widehat{O'FA}$$\Rightarrow EOO'F$ nội tiếp
a) $\widehat{OEA}=\widehat{OAE}$;$\widehat{O'AF}=\widehat{O'FA}$mà $\widehat{OAE}=\widehat{O'AF}$$\Rightarrow \widehat{OEA}=\widehat{O'FA}$$\Rightarrow EOO'F$ nội tiếp
a) $\widehat{OEA}=\widehat{OAE}$;$\widehat{O'AF}=\widehat{O'FA}$mà $\widehat{OAE}=\widehat{O'AF}$$\Rightarrow \widehat{OEA}=\widehat{O'FA}$$\Rightarrow EOO'F$ nội tiếp