The radius of the sector is 3cm, and the central angle is 120°. Then the arc length of the sector is the circumference of the circle. (fill in a fraction)
扇形的半径是3cm，圆心角是120°，那么这个扇形所对的弧长是圆周长的多少．(填几分之几)
<gadget id="calculator">120 / 360</gadget>
<output>1/3 = around 0.333333</output>

<result>1/3 = around 0.333333</result>