$\text{Ta có: $\widehat{xTB}$ = $\widehat{TBn}$ (= $110^o$)}$
$\text{mà đó là hai góc slt}$
$\text{nên Tx // Bn}$
$\text{gọi Bm là tia đối của Bn (Bn // Tx nên Bm // Tx)}$
$\text{$\widehat{xTB}$ + $\widehat{TBm}$ = $180^o$ (tcp)}$
$\text{T/S: $110^o$ + $\widehat{TBm}$ = $180^o$}$
$\text{⇒ $\widehat{TBm}$ = $70^o$}$
$\text{Ta có: Tx // Bm}$
$\text{Tx // Ly}$
$\text{Nên Bm // Ly (T/c 3 quan hệ từ vuông góc đến song song)}$
$\text{⇒ $\widehat{yLB}$ + $\widehat{LBm}$ = $180^o$ (tcp)}$
$\text{T/S: $150^o$ + $\widehat{LBm}$ = $180^o$}$
$\text{⇒ $\widehat{LBm}$ = $30^o$}$
$\text{$\widehat{TBL}$ = $\widehat{TBm}$ + $\widehat{LBm}$ = $70^o$ + $30^o$ = $100^o$}$
$\text{Vậy $\widehat{TBL}$ = $100^o$}$
$\text{HỌC TỐT!}$
$Thanhnhung_♩$
