Divide a circular piece of paper into several equal parts along its radius and cut them out, and use them to form an approximate rectangle with a constant area. The perimeter of this rectangle is 16.56 cm, and the width of the rectangle is equal to that of the circular paper If the radii are equal, what is the area of the circle in square centimetres?
把一个圆形纸片沿着它的半径平均分成若干份以后剪开，用它们拼成一个面积不变的近似的长方形，这个长方形的周长是16.56厘米，长方形的宽与圆形纸片的半径相等，这个圆形纸片的面积是多少平方厘米．
<gadget id="calculator">3.14 * 2</gadget>
<output>6.28</output>

<gadget id="calculator">2 + 6.28</gadget>
<output>8.28</output>

<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>