A cow is tied to a stake at the foot of a wall. The rope is 15 meters long. What is the largest area that the cow grazes in square meters?
在一堵围墙脚下的一枚木桩上拴着一头牛，牛绳长15米，这头牛吃草的最大的面积是多少平方米？
<gadget id="calculator">15 ** 2</gadget>
<output>225</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3.14 * 225 * (1/2)</gadget>
<output>353.25</output>

<result>353.25</result>