In a circle, make a square with its radius as the side length. The area of the square is 36cm**2. What is the area of the circle in cm**2?
在一个圆内，以它的半径为边长做一个正方形，已知正方形面积是36cm**2，圆的面积是多少cm**2．
<gadget id="calculator">3.14 * 36</gadget>
<output>113.04</output>

<result>113.04</result>