a. \(S_{ABCD} = AC.BD = \dfrac{1}{2}.12.16 = 96\) \((cm^2)\)
b.Trong tam giác vuông \(OAB\) ta có:
\(\begin{array}{l}A{B^2} = O{A^2} + O{B^2} \\= {\left( {\dfrac{{AC}}{2}} \right)^2} + {\left( {\dfrac{{BD}}{2}} \right)^2} \\= {6^2} + {8^2} = 100\\ \Rightarrow AB = 10(cm)\end{array}\)
c. Kẻ \(AH ⊥ CD\) (\(H ∈ CD\))
\(\eqalign{ & {S_{ABCD}} = AH.CD \cr & \Rightarrow AH = {{{S_{ABCD}}} \over {CD}} = {{96} \over {10}} = 9,6(cm) \cr} \)
