Draw the largest circle inside a square. Given that the area of the square is 20 square centimeters, what is the area of the circle?
在一个正方形内画一个最大的圆，已知正方形的面积是20平方厘米，圆的面积是多少？
<gadget id="calculator">3.14 * 5</gadget>
<output>15.7</output>

<result>15.7</result>