9A:
a: \(\widehat{xOy};\widehat{zOy}\)
b: \(\widehat{xOy}+\widehat{yOz}=180^0\)(hai góc kề bù)
=>\(\widehat{yOz}+70^0=180^0\)
=>\(\widehat{yOz}=110^0\)
c: Ot là phân giác của góc xOy
=>\(\widehat{xOt}=\dfrac{1}{2}\cdot\widehat{xOy}=\dfrac{1}{2}\cdot70^0=35^0\)
\(\widehat{xOt}+\widehat{zOt}=180^0\)(hai góc kề bù)
=>\(\widehat{zOt}+35^0=180^0\)
=>\(\widehat{zOt}=145^0\)
9B:
a: \(\widehat{mOn};\widehat{aOn}\)
b: \(\widehat{mOn}+\widehat{aOn}=180^0\)(hai góc kề bù)
=>\(\widehat{aOn}=180^0-120^0=60^0\)
c: Ob là phân giác của góc mOn
=>\(\widehat{mOb}=\dfrac{1}{2}\cdot\widehat{mOn}=\dfrac{1}{2}\cdot120^0=60^0\)
\(\widehat{mOb}+\widehat{bOa}=180^0\)(hai góc kề bù)
=>\(\widehat{bOa}+60^0=180^0\)
=>\(\widehat{bOa}=120^0\)
