What is the length of the arc subtended by a circle whose central angle is 60° and whose radius is 9 cm?
一个圆心角为60°，半径为9cm，所对的弧长为多少cm．
<gadget id="calculator">60 * 3.14 * 9</gadget>
<output>1_695.6</output>

<gadget id="calculator">1_695.6 / 180</gadget>
<output>9.42</output>

<result>9.42</result>