If the radius of the sector is expanded to 3 times of the original, and the central angle is reduced to 1/3 of the original, then the area is reduced to the original
扇形半径扩大为原来的3倍，圆心角缩小为原来的(1/3)，则面积缩小为原来的多少
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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