Câu 6:
\(\left\{{}\begin{matrix}\widehat{ACB}\text{ chung}\\\widehat{CKB}=\widehat{CHA}=90^0\end{matrix}\right.\Rightarrow\Delta CHA\sim\Delta CKB\left(g.g\right)\\ \left\{{}\begin{matrix}\widehat{ACB}\text{ chung}\\\widehat{AHC}=\widehat{DBC}=90^0\end{matrix}\right.\Rightarrow\Delta CHA\sim\Delta CBD\left(g.g\right)\\ \left\{{}\begin{matrix}\widehat{ACB}\text{ chung}\\\widehat{CKB}=\widehat{DBA}=90^0\end{matrix}\right.\Rightarrow\Delta CKB\sim\Delta CBD\left(g.g\right)\\ \Delta CHA\sim\Delta CKB\Rightarrow\dfrac{CH}{CK}=\dfrac{CA}{CB}\Rightarrow\Delta CKH\sim\Delta CBA\left(c.g.c\right)\)