$\text{Vẽ Cz // By}$
$\text{Cz // By}$
$\text{nên $\widehat{CBy}$ + $\widehat{BCz}$ = $180^o$ (tcp)}$
$\text{T/S: $150^o$ + $\widehat{BCz}$ = $180^o$}$
$\text{⇒ $\widehat{BCz}$ = $180^o$ - $150^o$ = $30^o$}$
$\text{Cz // By (gt)}$
$\text{Ax // By (gt)}$
$\text{nên Ax // Cz (T/c 3 quan hệ từ vuông góc đến song song)}$
$\text{⇒ $\widehat{CAx}$ = $\widehat{ACz}$ = $40^o$ (slt)}$
$\text{$\widehat{BCz}$ + $\widehat{ACz}$ = $\widehat{ACB}$}$
$\text{T/S: $30^o$ + $40^o$ = $70^o$}$
$\text{Vậy $\widehat{ACB}$ = $70^o$}$
$\text{CHÚC BẠN HỌC TỐT NHÉ!}$
