The length of an arc is equal to (4/9) of the circumference of the circle it is on, what is the central angle subtended by this arc?
一段弧长等于它所在圆的周长的(4/9)，那么这段弧所对的圆心角是多少度．
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">360 * (4/9)</gadget>
<output>160</output>

<result>160</result>