Giải thích các bước giải:
a.Ta có:
$\sin \widehat{ACB}=\dfrac{AB}{AC}$
$\to \sin54^o=\dfrac{AB}8$
$\to AB=8\sin54^o$
b.Áp dụng định lý sin cho $\Delta ACD$ ta có;
$\dfrac{AD}{\sin\widehat{ACD}}=\dfrac{AC}{\sin\widehat{ADC}}$
$\to \sin\widehat{ADC}=\dfrac{AC}{AD}\cdot \sin\widehat{ACD}$
$\to \sin\widehat{ADC}=\dfrac{8}{9.6}\cdot \sin74^o$
$\to \sin\widehat{ADC}\approx 0.8$
$\to \widehat{ADC}\approx 53^o$
