In a circle, make a square with its radius as the side length. The area of the square is 10 square centimeters. What is the area of the circle in square centimeters?
在一个圆内，以它的半径为边长做一个正方形，已知正方形的面积是10平方厘米，圆的面积是多少平方厘米．
<gadget id="calculator">3.14 * 10</gadget>
<output>31.4</output>

<result>31.4</result>