b) + Xét Δ ABC có \(\widehat{BAC}=90\text{°}\)
\(\Rightarrow\) \(BC^2=AB^2+AC^2\) ( định lý Pytago )
\(\Rightarrow\) \(BC^2=6^2+8^2\)
\(\Rightarrow\) \(BC^2=100\)
\(\Rightarrow\) BC = 10 ( cm )
+ Δ HBA \(\sim\) Δ ABC ( cmt )
\(\Rightarrow\) \(\frac{AH}{AC}=\frac{AB}{BC}\)
\(\Rightarrow\) \(\frac{AH}{8}=\frac{6}{10}\)
\(\Rightarrow\) AH = 4,8 cm
a) + Δ ABC và Δ HBA có
\(\widehat{CAB}=\widehat{AHB}=90\text{°}\)
\(\widehat{B}\) góc chung
\(\Rightarrow\) Δ ABC ∼ Δ HBA ( g.g )
+ Δ AHC ∼ Δ BAC ( g.g ) (cmtt)
+ Vì Δ ABC ∼ Δ HBA ( cmt )
Δ AHC ∼ Δ BAC ( cmt )
\(\Rightarrow\) Δ AHC ∼ Δ BHA ( t/c Δ ∼ )
