Simone
(1)\overrightarrow{AB}= (4,4)，\overrightarrow{AD}= (-2,1)，，\overrightarrow{AC}= \overrightarrow{AB}+ \overrightarrow{AD}= (2,5)，点C的坐标为(1,\, 3)．
（2）\mathrel{|} \overrightarrow{AB}\mathrel{|} = 4\sqrt{2}，\mathrel{|} \overrightarrow{AD}\mathrel{|} = \sqrt{5}，．
\cos \lt \overrightarrow{AB}，\overrightarrow{AD}\gt = \dot{\mathrel{|} \overrightarrow{AB}\mathrel{|} \cdot \mathrel{|} \overrightarrow{AD}\mathrel{|} }= -\dfrac{\sqrt{10}}{10}，，
\sin \lt \overrightarrow{AB}，\overrightarrow{AD}\gt = \dfrac{3\sqrt{10}}{10}，，
∴S_{ABCD}= \mathrel{|} \overrightarrow{AB}\mathrel{|} \cdot \mathrel{|} \overrightarrow{CD}\mathrel{|} \cdot \sin \lt \overrightarrow{AB}，\overrightarrow{CD}\gt = 12，．
