4. As shown in the figure, in rectangle $A B C D$, $\triangle A E D$ and $\triangle B F C$ are both isosceles right triangles, $E F=A D=2$. Then the area of rectangle $A B C D$ is $\qquad$ .
【Answer】 8
【Solution】The rectangle can be cut as shown in the figure below. Since $E F=A D=2 A G$, the area of the entire rectangle is 8 times the area of the small square. Since the area of one small square is 1, the area of the rectangle is 8.