Cut a circle with the largest area on a piece of rectangular paper with a length of 6 cm and a width of 4 cm. What is the area of this circle in cm**2.
在一张长6厘米，宽4厘米的长方形纸上剪一个面积最大的圆，这个圆的面积是多少cm**2．
<gadget id="calculator">4 / 2</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>