The radius of a circle is equal to the side length of a square. If the area of the square is 9 square meters, what is the area of the circle in square meters?
一个圆的半径与正方形的边长相等，如果正方形的面积是9平方米，那么这个圆的面积是多少平方米．
<gadget id="calculator">9 * 3.14</gadget>
<output>28.26</output>

<result>28.26</result>