a) Ta có:
$+)\widehat{xOy}+\widehat{xOy'}=180^o$
$50^o+\widehat{xOy'}=180^o$
$⇒\widehat{xOy'}=180^o-50^o=130^o$
$+)\widehat{xOy}+\widehat{x'Oy}=180^o$
$50^o+\widehat{x'Oy}=180^o$
$⇒\widehat{x'Oy}=180^o-50^o=130^o$
$+)\widehat{x'Oy}+\widehat{x'Oy'}=180^o$
$130^o+\widehat{x'Oy'}=180^o$
$⇒\widehat{x'Oy'}=180^o-130^o=50^o$
b) Các góc bằng nhau là:
$\widehat{xOy}=\widehat{x'Oy'}=50^o$
$\widehat{xOy'}=\widehat{x'Oy}=130^o$