Tính độ dài cạnh HC, BC

$$\begin{gathered} bt1: cho ∆ ABC nhọn , kẻ Ac vuông góc BC ( H\in BC) \\ bik AC =20cm ,AH=12cm,BH=5cm \mathit{.}\mathit{T}\mathit{í}\mathit{n}\mathit{h}\mathit{ }\mathit{đ}\mathit{ộ}\mathit{ }\mathit{d}\mathit{à}\mathit{i}\mathit{ }\mathit{c}\mathit{ạ}\mathit{n}\mathit{h}\mathit{ }\mathit{H}\mathit{C}\mathit{,}\mathit{B}\mathit{C} \end{gathered}$$