When drawing a circle, when the distance between the two corners of the compass is 4 cm, what is the circumference of the circle drawn?
画圆时，圆规两角间的距离为4厘米时，所画出的圆的周长是多少厘米．
<gadget id="calculator">3.14 * 4 * 2</gadget>
<output>25.12</output>

<result>25.12</result>