If an arc is (2/5) the length of the circumference of a circle, what is the central angle subtended by the length of this arc?
一条弧是圆周长的(2/5)，则此条弧长所对的圆心角是多少度．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">360 * (2/5)</gadget>
<output>144</output>

<result>144</result>