$\widehat{xOy}=50^{0}, \widehat{xOz}=75^{0}, \widehat{xOt}=100^{0}$
$⇒\widehat{xOy}<\widehat{xOz}<\widehat{xOt}⇒Ot$ nằm giữ 2 tia $Ox, Oy$
$\widehat{xOz}+\widehat{zOt}=\widehat{xOt}$
$⇒\widehat{zOt}=\widehat{xOt}-\widehat{xOz}=100^{0}-50^{0}=50^{0}$
Vì $+Oz$ nằm giữ 2 tia $Ox, Oy$
$+\widehat{zOt}=\widehat{xOz}$
$⇒Oz$ là tia phân giác của $\widehat{xOt}$