Giải thích các bước giải:

a.Các cặp góc đối đỉnh:

$\widehat{xOy},\widehat{x'Oy'}$

$\widehat{xOy'},\widehat{x'Oy}$

Cặp góc kề bù:

$\widehat{xOy},\widehat{yOx'}$

$\widehat{yOx'},\widehat{x'Oy'}$

$\widehat{x'Oy'},\widehat{y'Ox}$

$\widehat{y'Ox},\widehat{xOy}$

b.Từ a 

$\to \widehat{xOy}+\widehat{x'Oy}=180^o$

$\to 3\widehat{x'Oy}+\widehat{x'Oy}=180^o$

$\to 4\widehat{x'Oy}=180^o$

$\to \widehat{x'Oy}=45^o$

$\to \widehat{ x'Oy'}=180^o-\widehat{x'Oy}=135^o$