The area of the square is 20 square centimeters, what is the area of the largest circle inside the square?
正方形的面积是20平方厘米，而正方形内最大圆面积是多少平方厘米
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 * 3.14</gadget>
<output>15.7</output>

<result>15.7</result>