The length of an arc is 15.7 cm, and the radius of the circle is 15 cm, what is the central angle subtended by the arc?
一弧长为15.7厘米，所在圆的半径为15厘米，则弧所对的圆心角为多少．
<gadget id="calculator">180 / 3.14 / 15</gadget>
<output>3.821656</output>

<gadget id="calculator">15.7 * 3.821656</gadget>
<output>59.999999</output>

<result>59.999999</result>