a) $Om$ là phân giác $\widehat{xOy}$
⇒ $\widehat{xOm}=\dfrac{\widehat{xOy}}{2}=\dfrac{60^o}{2}=30^o$
b) $Om$ là phân giác $\widehat{xOy}$
⇒ $\widehat{xOm}=\widehat{yOm}$
$On$ là phân giác $\widehat{yOz}$
⇒ $\widehat{yOn}=\widehat{zOn}$
Ta có: $\widehat{xOy}+\widehat{yOz}=180^o$
⇒ $(\widehat{xOm}+\widehat{yOm})+(\widehat{yOn}+\widehat{zOn})=180^o$
$2.\widehat{yOm}+2.\widehat{yOn}=180^o$
$2.(\widehat{yOm}+\widehat{yOn})=180^o$
⇒ $\widehat{yOm}+\widehat{yOn}=90^o$
⇒ $\widehat{mOn}=90^o$
Vậy $\widehat{xOm}=30^o$, $\widehat{mOn}=90^o$