A cow is tied to a stake with a rope length of 3.5 meters. What is the maximum area that the cow can eat grass?
一头牛拴在一个木桩上，绳长3.5米，这头牛能吃到草的最大面积是多少？
<gadget id="calculator">3.5 ** 2</gadget>
<output>12.25</output>

<gadget id="calculator">3.14 * 12.25</gadget>
<output>38.465</output>

<result>38.465</result>