In a square with a side length of 4 cm, cut the largest circle, what is the area of the circle in cm**2.
在一个边长为4cm的正方形中，剪一个最大的圆，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>