a, \begin{cases}\widehat{ABH}=\widehat{BDC} \\ \widehat{AHB}=\widehat{BCD} \end{cases} => dpcmb, \begin{cases}\frac{1}{AH^2}=\frac{1}{AD^2}+\frac{1}{AB^2} \\ \end{cases}=> tính dc AHc, Sabc = AB*BC
a, \begin{cases}\widehat{ABH}=\widehat{BDC} \\ \widehat{AHB}=\widehat{BCD} \end{cases} => dpcmb, \begin{cases}\frac{1}{AH}=\frac{1}{AD}+\frac{1}{AB} \\ \end{cases}=> tính dc AHc, Sabc = AB*BC
a, \begin{cases}\widehat{ABH}=\widehat{BDC} \\ \widehat{AHB}=\widehat{BCD} \end{cases} => dpcmb, \begin{cases}\frac{1}{AH
^2}=\frac{1}{AD
^2}+\frac{1}{AB
^2} \\ \end{cases}=> tính dc AHc, Sabc = AB*BC