Đáp án:
$\widehat{B}=60^o; \widehat{C}=30^o$
Giải thích các bước giải:
$\cos \widehat{B}=\dfrac{AB}{BC}\\ \sin \widehat{C}=\dfrac{AB}{BC}\\ 2\cos \widehat{B}-\sin \widehat{C}=\dfrac{1}{2}\\ \Leftrightarrow 2\dfrac{AB}{BC}-\dfrac{AB}{BC}=\dfrac{1}{2}\\ \Leftrightarrow \dfrac{AB}{BC}=\dfrac{1}{2}\\ \Leftrightarrow \cos \widehat{B}=\sin \widehat{C}=\dfrac{1}{2}\\ \Rightarrow \widehat{B}=60^o; \widehat{C}=30^o$