The radius of the sector is 3cm, the central angle is 120°, and the corresponding arc length is the circumference of the circle (fill in a fraction).
扇形的半径是3cm，圆心角是120°，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>