Ta có: \(\dfrac{AH}{AK}=\dfrac{3AB}{3AC}=\dfrac{AB}{AC}.\)
\(\Rightarrow\dfrac{AH}{AK}=\dfrac{AB}{AC}.\Rightarrow\dfrac{AH}{AB}=\dfrac{AK}{AC}.\)
Xét \(\Delta AHK\) và \(\Delta ABC:\)
\(\dfrac{AH}{AB}=\dfrac{AK}{AC}\left(cmt\right).\\ \widehat{A}chung.\)
\(\Rightarrow\Delta AHK\sim\Delta ABC\left(c-g-c\right).\)
\(\Rightarrow\dfrac{HK}{BC}=\dfrac{AH}{AB}=\dfrac{AK}{AC}=\dfrac{3AC}{AC}=3.\)
Tỉ số đồng dạng bằng 3.
Đúng 1
Bình luận (0)
