nói thật chứ bài nay tui lop 7 lam dc
ban giup mk giai bai tren dc k mk dang can
a) Ta thấy ngay \(\Delta ABH\sim\Delta CBA\left(g-g\right)\)
\(\Rightarrow\frac{AB}{BC}=\frac{AH}{AC}\Rightarrow AH.BC=AB.AC\)
b)
Vì \(\Delta ABH\sim\Delta CBA\left(g-g\right)\)
\(\Rightarrow\frac{AB}{BC}=\frac{BH}{AB}\Rightarrow AB^2=BH.BC\)
c)
Vì \(\Delta ACH\sim\Delta BCA\left(g-g\right)\)
\(\Rightarrow\frac{AC}{BC}=\frac{CH}{AC}\Rightarrow AC^2=CH.BC\)
d) Ta có \(\Delta ACH\sim\Delta BCA\left(g-g\right)\)
\(\Rightarrow\frac{AC}{BC}=\frac{AH}{BA}\Rightarrow\frac{1}{AH}=\frac{BC}{AB.AC}\Rightarrow\frac{1}{AH^2}=\frac{BC^2}{AB^2.AC^2}\)
\(\Rightarrow\frac{1}{AH^2}=\frac{AB^2+AC^2}{AB^2.AC^2}\Rightarrow\frac{1}{AH^2}=\frac{1}{AB^2}+\frac{1}{AC^2}\)
