a, Các cặp góc kề bù là:
\(\left(\widehat{xOa};\widehat{xOb}\right);\left(\widehat{xOb};\widehat{yOb}\right);\left(\widehat{yOb};\widehat{yOa}\right)\)
b, Ta có:
\(\widehat{xOa}=\widehat{yOb}\left(d.d\right)\Rightarrow\widehat{yOb}=80^o\)
\(\widehat{xOa}+\widehat{xOb}=180^o\Rightarrow\widehat{xOb}=180^o-80^o=100^o\)
mà \(\widehat{xOb}=\widehat{yOa}\left(d.d\right)\Rightarrow\widehat{yOa}=100^o\)
Vậy.............
Chúc bạn học tốt!!!