Vì\(\widehat{xOy}\)và\(\widehat{yOz}\)là hai góc kề bù
Do đó\(\widehat{xOy}+\widehat{yOz}=180^o\)
Hay\(120^o+\widehat{yOz}=180^o\)
\(\Rightarrow\widehat{yOz}=180^o-120^o\)
\(\Rightarrow\widehat{yOz}=60^o\)
Vì tia Ot là tia phân giác của\(\widehat{yOz}\)
\(\Rightarrow\widehat{yOt}=\widehat{zOt}=\frac{\widehat{yOz}}{2}=\frac{60^o}{2}=30^o\)
Vì tia Ot nằm giữa \(\widehat{yOz}\)
Vì Oy nằm giữa\(\widehat{xOz}\)
Do đó tia Oy nằm giữa \(\widehat{xOt}\)
Nên\(\widehat{xOy}+\widehat{yOt}=\widehat{xOt}\)
Hay\(120^o+30^o=\widehat{xOt}\)
\(\Rightarrow\widehat{xOt}=150^o\)