There is a square grassland with a side length of 4 meters, and a tree at each opposite corner. A sheep is tied to each tree, and the rope is 4 meters long. How many square meters of grassland can the two sheep eat?
有一块正方形草地，边长4米，两对角各有1棵树，树上各拴一只羊，绳子长4米，那么两只羊都吃到的草地面积有多少平方米．
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">3.14 * 8</gadget>
<output>25.12</output>

<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">25.12 - 16</gadget>
<output>9.12</output>

<result>9.12</result>