$ (2)解：由图已知点A(-2,0)，点C(0,2)$
$设AC解析式为y=kx+2将点A代入解得$
$k=1$
$AC解析式为y=x+2$
$D到AC的距离为\frac {|-1-\sqrt{3}+2|}{\sqrt{1+1}}=\frac {\sqrt{3}-1}{\sqrt{2}}$
$AC=\sqrt{OC^2+OA^2}=2\sqrt{2}$
$S_{△ACD}=\frac12×2\sqrt{2}×\frac {\sqrt{3}-1}{\sqrt{2}}$
$=\sqrt{3}-1$
