Cut the largest circle out of a square cardboard with a circumference of 36 cm and find the area of the circle.
在周长是36厘米的正方形纸板上剪下一个最大的圆，求这个圆的面积．
<gadget id="calculator">36 / 4</gadget>
<output>9</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">(9/2) ** 2</gadget>
<output>81/4 = around 20.25</output>

<gadget id="calculator">3.14 * (81/4)</gadget>
<output>63.585</output>

<result>63.585</result>