On a square lawn with a side length of 4 meters, there is a tree at the two vertices of a diagonal line, and a sheep is tied to each tree. The rope is 4 meters long. What is the area of the grass that can be eaten by two sheep? rice.
一块边长是4米的正方形草地上，一条对角线的两个顶点各有1棵树，树上各栓1只羊，绳长4米，两头羊都能吃到的草地面积为多少平方米．
<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>