If the radius of a circle is 6 cm, then the arc length subtended by the central angle of 30° = how many cm.
如果圆的半径为6厘米，那么30°的圆心角所对的弧长=多少厘米．
<gadget id="calculator">30 * 3.14 * 6</gadget>
<output>565.2</output>

<gadget id="calculator">565.2 / 180</gadget>
<output>3.14</output>

<result>3.14</result>