What is the largest circle to be cut out of a square with a side length of 4 cm?
要在一个边长是4厘米的正方形中剪去一个最大的圆，这个圆的面积是多少平方厘米
<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>