Draw a circle with a compass. If the distance between the two feet of the compass is 4 cm, what is the circumference of the circle in cm?
用圆规画一个圆，如果圆规两脚之间距离是4厘米，这个圆的周长是多少厘米．
<gadget id="calculator">2 * 3.14 * 4</gadget>
<output>25.12</output>

<result>25.12</result>