If the radius of a circle is 5 cm, what is the arc length subtended by the central angle of 72°?
如果圆的半径为5cm，那么72°圆心角所对的弧长是多少．
<gadget id="calculator">72 * 3.14 * 5</gadget>
<output>1_130.4</output>

<gadget id="calculator">1_130.4 / 180</gadget>
<output>6.28</output>

<result>6.28</result>