Divide a circle into several equal parts and put together an approximate parallelogram. If the base of this parallelogram is 6.28 cm, what is the area of the circle in square centimeters?
把一个圆平均分成若干份，拼成一个近似的平行四边形，如果这个平行四边形的底是6.28厘米，那么这个圆的面积是多少平方厘米？
<gadget id="calculator">6.28 / 3.14</gadget>
<output>2</output>

<gadget id="calculator">2 * 2 * 3.14</gadget>
<output>12.56</output>

<result>12.56</result>