Divide a circle into several equal parts and form an approximate rectangle. The perimeter of the rectangle is 16.56 cm. Find the area of the original circle.
把一个圆平均分成若干份，拼成一个近似的长方形后，长方形的周长是16.56厘米，求原来圆的面积．
<gadget id="calculator">16.56 / 8.28</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>