Giải thích các bước giải:
Ta có:
$\begin{array}{l}
\left\{ \begin{array}{l}
\widehat Achung\\
\widehat {AEH} = \widehat {AHC} = {90^0}
\end{array} \right.\\
\Rightarrow \Delta AEH \sim \Delta AHC\left( {g.g} \right)\\
\Rightarrow \dfrac{{AE}}{{AH}} = \dfrac{{AH}}{{AC}}\\
\Rightarrow AE.AC = A{H^2}\left( 1 \right)
\end{array}$
Và:
$\begin{array}{l}
\left\{ \begin{array}{l}
\widehat Achung\\
\widehat {ADH} = \widehat {AHB} = {90^0}
\end{array} \right.\\
\Rightarrow \Delta ADH \sim \Delta AHB\left( {g.g} \right)\\
\Rightarrow \dfrac{{AD}}{{AH}} = \dfrac{{AH}}{{AB}}\\
\Rightarrow AD.AB = A{H^2}\left( 2 \right)
\end{array}$
Từ $\left( 1 \right),\left( 2 \right) \Rightarrow AD.AB = AE.AC$