Use a compass to draw a circle with a diameter of 8 cm. What is the distance between the two feet of the compass in cm?
用圆规画一个直径为8厘米的圆，圆规两脚间的距离应取多少厘米．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<result>4</result>