a) Có : \(\widehat{xOy}+\widehat{yOz}=180^o\)(kề bù)
\(\Rightarrow80^o+\widehat{yOz}=180^o\)
\(\Rightarrow\widehat{yOz}=100^o\)
b) Ot là tia pg góc yOz
\(\Rightarrow\widehat{tOy}=\frac{\widehat{yOz}}{2}=\frac{100^o}{2}=50^o\)
Ot' là tia pg góc xOy
\(\Rightarrow\widehat{yOt'}=\frac{\widehat{xOy}}{2}=\frac{80^o}{2}=40^o\)
- Có : \(\widehat{tOt'}=\widehat{tOy}+\widehat{yOt'}\)
\(\Rightarrow\widehat{tOt'}=50^o+40^o=90^o\)
=> Góc tOt' là góc vuông
#H