Divide a circle into several equal sectors, and then cut and assemble it into an approximate rectangle. Given that the perimeter of the rectangle is 16.56 cm, what is the area of the circle?
把一个圆分成若干个相等的扇形，然后把它剪拼成一个近似的长方形．已知长方形的周长是16.56厘米，这个圆的面积是多少．
<gadget id="calculator">16.56 / 8.28</gadget>
<output>2</output>

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

<result>12.56</result>