There is a square piece of red paper with an area of 40 square centimeters. Now use it to cut into the largest circular board newspaper. What is the area in square centimeters of the unused part? (π takes 3.14).
有一块正方形红纸，它的面积是40平方厘米．现在要用它剪成一个最大的圆形办板报．剪掉不用的部分面积是多少平方厘米？(π取3.14)．
<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<gadget id="calculator">3.14 * 10</gadget>
<output>31.4</output>

<gadget id="calculator">40 - 31.4</gadget>
<output>8.6</output>

<result>8.6</result>