A sheep is tied to the grass, the length of the rope is 7.2m, and the joint is 0.2m. What is the maximum area of grass that the sheep can eat?
草地上拴着一只羊，绳长7.2m，接头处是0.2m，这只羊最多可吃到的草地的面积是多少平方米？
<gadget id="calculator">7.2 - 0.2</gadget>
<output>7</output>

<gadget id="calculator">7 ** 2</gadget>
<output>49</output>

<gadget id="calculator">3.14 * 49</gadget>
<output>153.86</output>

<result>153.86</result>