Hình bạn tự vẽ nha.
2.a) Xét \(\Delta AHB\), có:
\(\widehat{HAB}+\widehat{AHB}+\widehat{B}=180^o\)(đ/l)
\(\Rightarrow\widehat{HAB}=180^o-\left(\widehat{AHB}+\widehat{B}\right)=180^o-\left(90^o+70^o\right)=20^o\)
Tương tự, xét \(\Delta AHC\), có:
\(\widehat{HAC}+\widehat{AHC}+\widehat{C}=180^o\)
\(\Rightarrow\widehat{HAC}=180^o-\left(\widehat{AHC}+\widehat{C}\right)180^o-\left(90^o+30^o\right)=60^o\)
b)Xét \(\Delta ABC\), có:
\(\widehat{BAC}+\widehat{B}+\widehat{C}=180^o\)(đ/l)
\(\Rightarrow\widehat{BAC}=180^o-\left(\widehat{B}+\widehat{C}\right)=180^o-\left(70^o+30^o\right)=80^o\)
Mà AD là tia phân giác của góc A(g/t)
\(\Rightarrow\widehat{ADC}=\widehat{ADB}=\dfrac{\widehat{BAC}}{2}=\dfrac{80^o}{2}=40^o\)
